Method for producing photomask and method for producing photomask pattern layout

ABSTRACT

An isolated light-shielding pattern formed from a light-shielding film region  101  and a phase shift region  102  is formed on a transparent substrate  100  serving as a mask. The phase shift region  102  has a phase difference with respect to a light-transmitting region of the transparent substrate  100 . Moreover, the width of the phase shift region  102  is set such that a light-shielding property of the phase shift region  102  becomes at least about the same as that of a light-shielding film having the same width.

TECHNICAL FIELD

The present invention relates to a pattern-exposure photomask for use inmanufacturing semiconductor devices or liquid crystal display devices, amethod for producing the same, and a patterning method using thephotomask, and also relates to a method for producing photomask patternlayout, and a method for producing mask-writing data.

BACKGROUND ART

In recent years, a large-scale integrated circuit (hereinafter, referredto as LSI) implemented with a semiconductor has been increasinglyreduced in size. As a result, a feature error or dimensional errorbetween a mask pattern and a produced pattern (e.g., a resist patternformed by pattern transfer for a resist film) have been increasinglyregarded as important in a lithography process, one of the LSImanufacturing processes.

Moreover, reduction in pattern dimension in the LSI has reached aboutthe resolution limit defined by a wavelength of a light source(hereinafter, referred to as wavelength λ), a numerical aperture of aprojection optical system of an aligner (hereinafter, referred to asnumerical aperture NA), and the like. As a result, a manufacturingmargin associated with the yield in LSI manufacturing, e.g., a depth offocus, has also been significantly reduced.

In a conventional patterning method, a resist pattern having aprescribed feature is formed as follows: a light-shielding pattern of aprescribed feature, i.e., a mask pattern, is formed on a transparentsubstrate using a light-shielding film of a metal such as chromium.Then, a wafer having a resist film applied thereto is exposed to lightusing the transparent substrate having the mask pattern thereon as amask, so that light intensity distribution having a profile similar tothe mask pattern feature is projected to the resist film. Thereafter,the resist film is developed, whereby the resist pattern having theprescribed feature is produced.

A reduction projection aligner is generally used in such a patterningmethod as described above. For patterning, the reduction projectionaligner conducts reduction projection exposure for a resist film of aphotosensitive resin formed on a wafer, i.e., a substrate, by using atransparent substrate including a mask pattern with the dimension of adesired pattern magnified several times, i.e., by using a photomask.

FIG. 32(a) shows an example of a pattern whose minimum dimension issufficiently larger than the resolution. FIG. 32(b) shows the simulationresult of light intensity distribution projected to, e.g., a resist filmupon forming the pattern of FIG. 32(a) using a conventional photomask.

More specifically, when the numerical aperture NA is 0.6 and thewavelength λ is 0.193 μm, the resolution is about 0.13 μm. However, theminimum dimension of the pattern of FIG. 32(a) is about 0.39 μm (aboutthree times the resolution). The conventional photomask has a maskpattern having the dimension of the pattern of FIG. 32(a) magnified bythe magnification M of the aligner (an inverse number of a reductionratio). In this case, as shown in FIG. 32(b), the implemented lightintensity distribution has a profile similar to the feature of thepattern of FIG. 32(a), i.e., the mask pattern. Note that FIG. 32(b)shows the light intensity distribution using contour lines of therelative light intensity in a two-dimensional relative coordinate system(i.e., the light intensity calculated with the exposure light intensitybeing regarded as 1).

FIG. 33(a) shows an example of a pattern whose minimum dimensioncorresponds to about the resolution. FIG. 33(b) shows the simulationresult of light intensity distribution projected to, e.g., a resist filmupon forming the pattern of FIG. 33(a) using a conventional photomask.

More specifically, when the numerical aperture NA is 0.6 and thewavelength λ is 0.193 μm, the resolution is about 0.13 μm. The minimumdimension of the pattern of FIG. 33(a) is also about 0.13 μm. Theconventional photomask has a mask pattern having the dimension of thepattern of FIG. 33(a) magnified by the magnification M. In this case, asshown in FIG. 33(b), the implemented light intensity distribution issignificantly distorted from the profile similar to the feature of thepattern of FIG. 32(a), i.e., the mask pattern. Note that FIG. 33(b) alsoshows the light intensity distribution using contour lines of therelative light intensity in a two-dimensional relative coordinatesystem.

More specifically, as the minimum dimension of the pattern is reduced toabout the resolution, the line width of the mask pattern on thephotomask is also reduced. Therefore, the exposure light is likely to bediffracted when passing through the photomask. More specifically, as theline width of the mask pattern is reduced, the exposure light is likelyto reach the backside of the mask pattern. As a result, the mask patterncannot sufficiently shield the exposure light, making it extremelydifficult to form a fine pattern.

In order to form a pattern having a dimension equal to or smaller thanabout the resolution, H. Y. Liu et al. proposes a patterning method(first conventional example) (Proc. SPIE, Vol. 3334, P. 2 (1998)). Inthis method, a light-shielding pattern of a light-shielding film isformed on a transparent substrate as a mask pattern, as well as a phaseshifter for inverting the light transmitted therethrough by 180 degreesin phase is provided in a light-transmitting region (a portion having nolight-shielding pattern) of the transparent substrate. This methodutilizes the fact that a pattern having a dimension equal to or smallerthan about the resolution can be formed by the light-shielding filmlocated between the light-transmitting region and the phase shifter.

Hereinafter, the patterning method according to the first conventionalexample will be described with reference to FIGS. 34(a) to (d).

FIG. 34(a) is a plan view of a first photomask used in the firstconventional example, and FIG. 34(b) is a cross-sectional view takenalong line I-I of FIG. 34(a). As shown in FIGS. 34(a) and (b), alight-shielding film 11 is formed on a first transparent substrate 10 ofthe first photomask, and first and second openings 12 and 13 are formedin the light-shielding film 11 such that a light-shielding film region11 a having a width smaller than (resolution×magnification M) isinterposed therebetween. The first transparent substrate 10 is recessedunder the second opening 13 so as to provide a phase difference of 180degrees between the light transmitted through the first transparentsubstrate 10 through the first opening 12 and the light transmittedthrough the first transparent substrate 10 through the second opening13. Thus, the portion of the first transparent substrate 10corresponding to the first opening 12 serves as a normallight-transmitting region, whereas the portion of the first transparentsubstrate 10 corresponding to the second opening 13 serves as a phaseshifter. Therefore, a pattern having a desired line width equal to orsmaller than about the resolution can be formed by the light-shieldingfilm region ha located between the first and second openings 12 and 13.

FIG. 34(c) is a plan view of a second photomask used in the firstconventional example. As shown in FIG. 34(c), a light-shielding pattern21 of a light-shielding film is formed on a second transparent substrate20 of the second photomask.

In the first conventional example, a desired pattern is formed bycombination of a line pattern formed by the light-shielding film region11 a of the first photomask of FIG. 34(a) and a pattern formed by thelight-shielding pattern 21 of the second photomask of FIG. 34(c).

More specifically, in the first conventional example, a substrate havinga positive resist film applied thereto is exposed to light using thefirst photomask of FIG. 34(a). Then, the substrate is adjusted inposition so that a desired pattern is formed by a latent image resultingfrom exposure using the first photomask and a latent image resultingfrom exposure using the second photomask of FIG. 34(c). After exposureis subsequently conducted using the second photomask, the resist film isdeveloped, whereby a resist pattern is formed. Thus, excessive patterns(patterns other than the desired pattern) resulting from developmentafter exposure with the first photomask only can be removed by exposurewith the second photomask. This enables formation of a pattern having aline width equal to or smaller than about the resolution, i.e., apattern that cannot be formed by exposure with the second photomaskonly.

FIG. 34(d) shows a resist pattern formed by the patterning method of thefirst conventional example, i.e., the patterning method using the firstand second photomasks of FIGS. 34(a) and 34(c).

As shown in FIG. 34(d), the exposed substrate 30 has a resist pattern 31formed thereon, and the resist pattern 31 has a line pattern 31 a havinga line width equal to or smaller than about the resolution.

In addition to the method of H. Y. Liu et al., Watanabe et al. proposesanother patterning method (second conventional example) (Proc. of the51st Annual Meeting of JSAP, P 490). In this method, a pattern having aline width smaller than the wavelength λ is formed without providing alight-shielding film between a light-transmitting region and a phaseshifter. This method utilizes the effect that a pattern is formed by theboundary between a normal transparent substrate portion, i.e., alight-transmitting region, and a phase shifter.

Hereinafter, the patterning method according to the second conventionalexample will be described with reference to FIG. 35.

FIG. 35 is a plan view of a photomask used in the second conventionalexample. As shown in FIG. 35, a plurality of phase shifters 41 areperiodically arranged on a transparent substrate 40 of the photomask.

In the second conventional example, the use of the phase shifters 41enables formation of a pattern in which a plurality of line patternseach having a line width smaller than the wavelength λ are arrangedperiodically.

However, in order to form a pattern having a line width equal to orsmaller than about the resolution, the first conventional example mustuse a phase shift mask (first photomask) in which a light-shielding filmregion having a width of (resolution×magnification M) or less is locatedbetween a phase shifter and a light-transmitting region both having awidth of (resolution×magnification M) or more. In other words, thepattern formed with the first photomask has a line width equal to orsmaller than about the resolution only when specific conditions aresatisfied. Therefore, an arbitrary pattern feature cannot be implementedwith the first photomask only.

Accordingly, in order to form a pattern having a complicated featurelike in the pattern layout of a normal LSI, exposure with a mask (secondphotomask) different from the phase shift mask is essential in the firstconventional example. This results in increase in mask costs, orreduction in throughput as well as increase in manufacturing costs dueto an increased number of lithography steps.

Moreover, a normal mask, i.e., a non-phase-shift mask, is used as thesecond photomask. Therefore, even if the exposures using the first andsecond photomasks are combined, the pattern formed by the secondphotomask has a dimension equal to or larger than about the resolution,whereby the patterns capable of being formed with a dimension equal toor smaller than about the resolution are limited. In other words, thefirst conventional example is used only when the phase shifter and thelight-transmitting region can be located adjacent to each other underthe aforementioned conditions, e.g., when only a gate pattern on anactive region is formed.

In contrast, the second conventional example, i.e., the method in whicha pattern is formed without providing a light-shielding film between alight-transmitting region and a phase shifter, can be used only when thepatterns each having a line width smaller than the wavelength λ arerepeated. Therefore, a pattern having an arbitrary feature or anarbitrary dimension cannot be formed by this method alone.

Moreover, in the second conventional example, a portion where the phasechanges abruptly must be provided at the boundary between thelight-transmitting region of the transparent substrate and the phaseshifter. However, by the conventional mask formation method in which aphase shifter is formed by wet etching the transparent substrate, thetransparent substrate cannot be etched vertically at the boundary of thephase shifter. Moreover, when the transparent substrate is etched, alateral region of the phase shifter in the transparent substrate is alsosubjected to etching, making it difficult to control the dimension ofthe phase shifter. As a result, it is extremely difficult to produce amask capable of forming a fine pattern with high precision.

In the second conventional example, the dimension of the pattern formedby utilizing the phase shift effect is limited to about half thewavelength λ. However, when a pattern having a larger dimension isformed with a mask pattern of a light-shielding film, the minimumpossible dimension of the pattern corresponds to about the resolution.Accordingly, in the case where patterning is conducted using a singlemask that simultaneously implements the phase shift effect and thelight-shielding effect of the light-shielding film, a possibledimensional range of the pattern is discontinuous. This significantlyreduces a process margin for forming a pattern of an arbitrary dimensionwith a single mask, and in some cases, makes it impossible to form apattern with a single mask.

DISCLOSURE OF THE INVENTION

In view of the foregoing description, it is an object of the presentinvention to enable any pattern feature with any dimension including adimension equal to or smaller than about the resolution to be formed byexposure using a single mask implementing a phase shift effect.

In order to achieve this object, the photomask according to theinvention is a photomask including an isolated light-shielding patternformed on a transparent substrate that is transparent to a light source.The light-shielding pattern is formed from a light-shielding film regionformed from a light-shielding film, and a phase shift region having aphase difference with respect to a light-transmitting region of thetransparent substrate which has no light-shielding pattern. A width ofthe phase shift region is set such that a light-shielding property ofthe phase shift region becomes at least about the same as that of thelight-shielding film having the same width.

According to the photomask of the invention, the light-shielding patternis formed from the light-shielding film region, and the phase shiftregion having a phase difference with respect to the light-transmittingregion, and the width of the phase shift region is set such that thelight-shielding property of the phase shift region becomes at leastabout the same as that of the light-shielding film having the samewidth. Therefore, the transmitted light reaching the backside of thelight-shielding film region of the light-shielding pattern due to thediffraction phenomenon can be cancelled by the light transmitted throughthe phase shift region. Accordingly, even when a pattern having adimension equal to or smaller than about the resolution is formed, lightintensity distribution having a profile similar to the feature of thelight-shielding pattern can be obtained. As a result, any patternfeature with any dimension including a dimension equal to or smallerthan about the resolution can be formed by exposure using only thephotomask of the invention implementing the phase shift effect.

In the photomask of the invention, a contour of the light-shielding filmregion is preferably the same as a feature of the light-shieldingpattern, and the phase shift region is preferably provided inside thelight-shielding film region.

Thus, the transmitted light reaching the backside of the periphery ofthe light-shielding pattern due to the diffraction phenomenon can bereliably cancelled by the light transmitted through the phase shiftregion.

In the photomask of the invention, the phase shift region is preferablyprovided at least at or inside a corner of the light-shielding pattern,or at or inside an end of the light-shielding pattern.

Thus, the transmitted light reaching the backside of the corner or endof the light-shielding pattern due to the diffraction phenomenon can bereliably cancelled by the light transmitted through the phase shiftregion.

Note that, in the specification, the term “corner” means a portionhaving an angle larger than zero degree and smaller than 180 degreeswhen measured on the pattern.

In the photomask of the invention, provided that the phase shift regionhas a width Wm, it is preferable that Wm·(0.4×λ/NA)×M (where λ is awavelength of the light source, NA is a numerical aperture of areduction projection optical system of an aligner, and M is amagnification of the reduction projection optical system).

This ensures that that the light-shielding property of the phase shiftregion becomes at least about the same as that of the light-shieldingfilm having the same width.

In the photomask of the invention, provided that the light-shieldingpattern in which the phase shift region is provided has a width Lm, itis preferable that Lm·(0.8×λ/NA)×M.

This enables a light-shielding effect of the light-shielding pattern tobe improved by providing the phase shift region in the light-shieldingpattern.

Provided that Lm·(0.8×λ/NA)×M and the phase shift region has a width Wm,it is preferable that Wm·((0.8×λ/NA)×M)−Lm and Wm·Lm.

This ensures improvement in the light-shielding effect of thelight-shielding pattern.

Provided that Lm·(0.8×λ/NA)×M and the phase shift region has a width Wm,it is preferable that0.5×((((0.8×λ/NA)×M)−Lm)/2)·Wm·1.5×((((0.8×λ/NA)×M)−Lm)/2) and Wm·Lm.

This enables significant improvement in the light-shielding effect ofthe light-shielding pattern.

In the photomask of the invention, the phase difference of the phaseshift region with respect to the light-transmitting region is preferably(170+360×n) to (190+360×n) degrees (where n is an integer) with respectto a wavelength of the light source.

This ensures improvement in the light-shielding effect of thelight-shielding pattern.

In the photomask of the invention, the phase difference of the phaseshift region with respect to the light-transmitting region is preferablyprovided by etching at least one of a portion corresponding to thelight-transmitting region and a portion corresponding to the phase-shiftregion in the transparent substrate.

Thus, the phase difference can be reliably provided between the phaseshift region and the light-transmitting region.

In the photomask of the invention, the phase difference of the phaseshift region with respect to the light-transmitting region is preferablyprovided by forming a phase shifter layer either on a portion other thanthe light-transmitting region or a portion other than the phase-shiftregion in the transparent substrate.

Thus, the phase difference can be reliably provided between the phaseshift region and the light-transmitting region. The phase shifter layermay either be formed under or above the light-shielding film region.

A patterning method according to the invention is a patterning methodusing the photomask of the invention, and includes the steps of: forminga resist film on a substrate; conducting pattern exposure to the resistfilm using the photomask; and developing the resist film subjected tothe pattern exposure so as to form a resist pattern.

According to the patterning method of the invention, the photomask ofthe invention is used. Therefore, even when a pattern having a dimensionequal to or smaller than about the resolution is formed, the resultantlight-shielding effect of the light-shielding pattern is about the sameas that obtained when a pattern having a dimension equal to or largerthan about the resolution is formed. As a result, any pattern featurewith any dimension including a dimension equal to or smaller than aboutthe resolution can be formed by exposure using only the photomask of theinvention.

In the patterning method of the invention, the step of conductingpattern exposure preferably uses an oblique incidence illuminationmethod.

This enables improvement in a process margin such as a depth of focusfor a fine pattern.

In the patterning method of the invention, the resist film is preferablyformed from a positive resist.

Thus, a fine resist pattern can be reliably formed by pattern exposureusing the photomask of the invention. A negative resist may be used inorder to form a fine resist-removed region like a hole pattern.

A method for producing a photomask according to the invention is amethod for producing a photomask including an isolated light-shieldingpattern formed on a transparent substrate that is transparent to a lightsource, the isolated light-shielding pattern being formed from alight-shielding film region and a phase shift region. The methodincludes the steps of: forming a light-shielding film on the transparentsubstrate; patterning the light-shielding film so as to form a contourof the light-shielding film region; and removing a portion of thelight-shielding film located in the phase shift region so as to form anopening. The phase shift region has a phase difference with respect to alight-transmitting region of the transparent substrate, and a width ofthe phase shift region is set such that a light-shielding property ofthe phase shift region becomes at least about the same as that of thelight-shielding film having the same width.

According to the photomask producing method of the invention, thepatterning step for forming the contour of the light-shielding filmregion is conducted independently of the patterning step for forming theopening serving as the phase shift region. This enables accuratedimensional control of the contour of the light-shielding film region,i.e., the light-shielding pattern, and the phase shift region. Thus, thephotomask of the invention can be reliably produced.

In the photomask producing method of the invention, the step of formingthe opening preferably includes the step of etching, after forming theopening, a portion of the transparent substrate located under theopening such that a phase difference of (170+360×n) to (190+360×n)degrees (where n is an integer) with respect to a wavelength of thelight source is provided between the portion and the light-transmittingregion.

Thus, the phase shift region can be formed so as to reliably improve thelight-shielding effect of the light-shielding pattern. In this case, thestep of forming the opening is preferably conducted prior to the step offorming the contour of the light-shielding film region. This enables thetransparent substrate to be etched using the light-shielding film withthe opening as a mask. This eliminates the need to conduct formation ofthe opening and etching of the substrate successively by using a resistpattern as in the case where the opening is formed after formation ofthe contour of the light-shielding film region. Accordingly, productionof the photomask of the invention is facilitated.

In the photomask producing method of the invention, the step of formingthe contour of the light-shielding film region preferably includes thestep of etching, after forming the contour of the light-shielding filmregion, a portion of the transparent substrate located outside thelight-shielding film region such that a phase difference of (170+360×n)to (190+360×n) degrees (where n is an integer) with respect to awavelength of the light source is provided between the portion and thephase shift region.

Thus, the phase shift region can be formed so as to reliably improve thelight-shielding effect of the light-shielding pattern. Moreover,production of the photomask of the invention is facilitated as comparedto the case where the phase difference is provided between thelight-transmitting region and the phase shift region by etching thetransparent substrate located under the opening having a small area.

In the photomask producing method of the invention, the step of formingthe light-shielding film preferably includes the step of forming underthe light-shielding film a phase shifter layer that provides phaseinversion of (170+360×n) to (190+360×n) degrees (where n is an integer)with respect to a wavelength of the light source, and the step offorming the opening preferably includes the step of removing, afterforming the opening, a portion of the phase shifter layer located underthe opening.

Thus, the phase shift region can be formed so as to reliably improve thelight-shielding effect of the light-shielding pattern. Moreover,management of the etching step is facilitated as compared to the casewhere the phase difference is provided between the light-transmittingregion and the phase shift region by etching the transparent substrate.Thus, the phase error is reduced as well as the phase shifter layer witha vertical edge can be easily formed. In this case, the step of formingthe opening is preferably conducted prior to the step of forming thecontour of the light-shielding film region. This enables the phaseshifter layer to be etched using the light-shielding film with theopening as a mask. This eliminates the need to conduct formation of theopening and etching of the shifter layer successively by using a resistpattern as in the case where the opening is formed after formation ofthe contour of the light-shielding film. Accordingly, production of thephotomask of the invention is facilitated.

In the photomask producing method of the invention, the step of formingthe light-shielding film preferably includes the step of forming underthe light-shielding film a phase shifter layer that provides phaseinversion of (170+360×n) to (190+360×n) degrees (where n is an integer)with respect to a wavelength of the light source, and the step offorming the contour of the light-shielding film region preferablyincludes the step of removing, after forming the contour of thelight-shielding film region, a portion of the phase shifter layerlocated outside the light-shielding film region.

Thus, the phase shift region can be formed so as to reliably improve thelight-shielding effect of the light-shielding pattern. Moreover,management of the etching step is facilitated as compared to the casewhere the phase difference is provided between the light-transmittingregion and the phase shift region by etching the transparent substrate.Thus, the phase error is reduced as well as the phase shifter layer witha vertical edge can be easily formed. Moreover, production of thephotomask of the invention is facilitated as compared to the case wherethe phase difference is provided between the light-transmitting regionand the phase shift region by removing the phase shifter layer locatedunder the opening having a small area. In this case, the step of formingthe contour of the light-shielding film region is preferably conductedprior to the step of forming the opening. This enables the phase shifterlayer to be etched using as a mask the light-shielding film having thecontour of the light-shielding film but having no opening. Thiseliminates the need to conduct formation of the contour of thelight-shielding film region and etching of the shifter layersuccessively by using a resist pattern as in the case where the contourof the light-shielding film region is formed after formation of theopening. Accordingly, production of the photomask of the invention isfacilitated.

In the photomask producing method of the invention, the step of formingthe opening is preferably conducted prior to the step of forming thecontour of the light-shielding film region, the method preferablyfurther includes, between the step of forming the opening and the stepof forming the contour of the light-shielding film region, the step offorming on the transparent substrate a phase shifter layer that providesphase inversion of (170+360×n) to (190+360×n) degrees (where n is aninteger) with respect to a wavelength of the light source, and the stepof forming the contour of the light-shielding film region preferablyincludes the step of removing, before forming the contour of thelight-shielding film region, a portion of the phase shifter layerlocated outside the light-shielding film region.

Thus, the phase shift region can be formed so as to reliably improve thelight-shielding effect of the light-shielding pattern. Moreover,management of the etching step is facilitated as compared to the casewhere the phase difference is provided between the light-transmittingregion and the phase shift region by etching the transparent substrate.Thus, the phase error is reduced as well as the phase shifter layer witha vertical edge can be easily formed. Moreover, if defects are producedin the step of patterning the phase shifter layer, it is possible torepair the defects by forming the phase shifter layer again. Therefore,the steps earlier than the step of forming the phase shifter layer neednot be repeated, improving the throughput.

In the photomask producing method of the invention, the step of formingthe contour of the light-shielding film region is preferably conductedprior to the step of forming the opening, the method preferably furtherincludes, between the step of forming the contour of the light-shieldingfilm region and the step of forming the opening, the step of forming onthe transparent substrate a phase shifter layer that provides phaseinversion of (170+360×n) to (190+360×n) degrees (where n is an integer)with respect to a wavelength of the light source, and the step offorming the opening preferably includes the step of removing, beforeforming the opening, a portion of the phase shifter layer located in thephase shift region.

Thus, the phase shift region can be formed so as to reliably improve thelight-shielding effect of the light-shielding pattern. Moreover,management of the etching step is facilitated as compared to the casewhere the phase difference is provided between the light-transmittingregion and the phase shift region by etching the transparent substrate.Thus, the phase error is reduced as well as the phase shifter layer witha vertical edge can be easily formed. Moreover, if defects are producedin the step of patterning the phase shifter layer, it is possible torepair the defects by forming the phase shifter layer again. Therefore,the steps earlier than the step of forming the phase shifter layer neednot be repeated, improving the throughput.

In the photomask producing method of the invention, provided that thephase shift region has a width Wm, it is preferable that Wm·(0.4×λ/NA)×M(where λ is a wavelength of the light source, NA is a numerical apertureof a reduction projection optical system of an aligner, and M is amagnification of the reduction projection optical system).

This ensures that that the light-shielding property of the phase shiftregion becomes at least about the same as that of the light-shieldingfilm having the same width.

In the photomask producing method of the invention, provided that thelight-shielding pattern in which the phase shift region is provided hasa width Lm, it is preferable that Lm·(0.8×λ/NA)×M.

This enables a light-shielding effect of the light-shielding pattern tobe improved by providing the phase shift region in the light-shieldingpattern.

Provided that Lm·(0.8×λ/NA)×M and the phase shift region has a width Wm,it is preferable that Wm·((0.8×λ/NA)×M)−Lm and Wm·Lm.

This ensures improvement in the light-shielding effect of thelight-shielding pattern.

Provided that Lm·(0.8×λ/NA)×M and the phase shift region has a width Wm,it is preferable that0.5×((((0.8×λ/NA)×M)−Lm)/2)·W·1.5×((((0.8×λ/NA)×M)−Lm)/2) and Wm·Lm.

This enables significant improvement in the light-shielding effect ofthe light-shielding pattern.

A method for producing pattern layout according to the invention is amethod for producing pattern layout of a photomask including an isolatedlight-shielding pattern formed on a transparent substrate that istransparent to a light source, the isolated light-shielding patternbeing formed from a light-shielding film region and a phase shiftregion. The method includes the steps of: extracting from the patterlayout corresponding to the light-shielding pattern a line patternhaving a width L×M equal to or smaller than (0.8×λ/NA)×M (where λ is awavelength of the light source, NA is a numerical aperture of areduction projection optical system of an aligner, and M is amagnification of the reduction projection optical system); and providinginside the extracted line pattern a phase shift region having a widthW×M equal to or smaller than ((0.8×λ/NA)−L)×M (where W·L).

According to the pattern-layout producing method of the invention, aline pattern having a width L×M equal to or smaller than (0.8×λ/NA)×M isextracted from the pattern layout corresponding to the light-shieldingpattern, and then a phase shift region having a width W×M equal to orsmaller than ((0.8×λ/NA)−L)×M (where W·L) is provided inside theextracted line pattern. Therefore, the phase shift region, i.e., maskenhancer, capable of enhancing the light-shielding effect can beprovided in the portion of the light-shielding pattern having a degradedlight-shielding effect, whereby the light intensity distribution can beprojected onto the wafer with a less distorted profile with respect tothe pattern layout. This enables production of the pattern layout of thephotomask capable of forming any pattern feature with any dimensionincluding a dimension equal to or smaller than about the resolution.

In the pattern layout producing method of the invention, it ispreferable that 0.5×(((0.8×λ/NA)−L)/2)·W·1.5×(((0.8×λ/NA)−L)/2) and W·L.

This enables significant improvement in the light-shielding effect ofthe light-shielding pattern.

In the pattern layout producing method of the invention, the step ofextracting the line pattern preferably includes the step of extracting apattern corner or a pattern end from the pattern layout, and the step ofproviding the phase shift region preferably includes the step ofproviding at or inside the extracted pattern corner, or at or inside theextracted pattern end, the phase shift region with four sides of(0.5×λ/NA)×M or less.

Thus, the transmitted light reaching the backside of the corner or endof the light-shielding pattern due to the diffraction phenomenon can bereliably cancelled by the light transmitted through the phase shiftregion.

A method for producing mask-writing data according to the invention is amethod for producing mask-writing data of a photomask including anisolated light-shielding pattern formed on a transparent substrate thatis transparent to a light source, the isolated light-shielding patternbeing formed from a light-shielding film region and a phase shift regionhaving a phase difference with respect to a light-transmitting region ofthe transparent substrate. The method includes the step of: extractingfrom pattern layout corresponding to the light-shielding pattern a linepattern having a width L×M equal to or smaller than (0.8×λ/NA)×M (whereλ is a wavelength of the light source, NA is a numerical aperture of areduction projection optical system of an aligner, and M is amagnification of the reduction projection optical system), and providinginside the extracted line pattern the phase shift region having a widthW×M equal to or smaller than ((0.8×λ/NA)−L)×M (where W·L) so as tomaximize a light-shielding effect of the light-shielding pattern, andthereafter, adjusting a dimension of the phase shift region based on aresult of test exposure or exposure simulation.

According to the mask-writing data producing method of the invention,the dimension of the phase shift region is adjusted based on the resultof test exposure or exposure simulation after the phase shift region isprovided so as to maximize the light-shielding effect of thelight-shielding pattern. Therefore, the dimension of the phase shiftregion can be adjusted so that the dimension of the pattern resultingfrom exposure with the photomask becomes equal to the design value.Accordingly, mask-writing data capable of preventing withdrawal of thepattern and the like can be produced, whereby a fine pattern can beaccurately formed by exposure with the photomask formed according to themask-writing data.

In the mask-writing data producing method of the invention, the step ofadjusting the dimension of the phase shift region preferably includesthe step of reducing a width of the phase shift region corresponding toa portion having a pattern width larger than a design value as a resultof exposure with the photomask, and increasing a width of the phaseshift region corresponding to a portion having a pattern width smallerthan the design value as a result of exposure with the photomask.

This ensures that the pattern resulting from exposure with the photomaskhas a dimension equal to the design value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the basic structure of a photomask accordingto a first embodiment of the invention;

FIG. 2 is a plan view of a desired design pattern to be formed on asubstrate to be exposed;

FIG. 3(a) is a plan view of a photomask of a first comparative examplefor forming the pattern of FIG. 2, FIG. 3(b) is a diagram showing thesimulation result of light intensity distribution projected to a resistfilm when the resist film is subjected to exposure using the photomaskof the first comparative example, and FIG. 3(c) is a diagram showing thecomparison result between a desired pattern feature and a profile of acontour line of the light intensity that represents the resist patternfeature in the simulation result of FIG. 3(b);

FIG. 4(a) is a plan view of the photomask of the first embodiment of theinvention for forming the pattern of FIG. 2, FIG. 4(b) is a diagramshowing the simulation result of light intensity distribution projectedto a resist film when the resist film is subjected to exposure using thephotomask of the first embodiment, and FIG. 4(c) is a diagram showingthe comparison result between a desired pattern feature and a profile ofa contour line of the light intensity that represents the resist patternfeature in the simulation result of FIG. 4(b);

FIG. 5(a) is a plan view of a photomask of a second comparative example,FIG. 5(b) is a plan view of a photomask of a third comparative example,FIGS. 5(c) to (e) are diagrams showing the simulation result of lightintensity distribution of the light transmitted between two points A andB of the photomasks of the second and third comparative examples,wherein the width L was 0.06 μm, 0.10 μm and 0.16 μm, respectively, andFIG. 5(f) is a diagram showing the simulation result of a change inlight intensity of the light transmitted through the center ofrespective isolated line patterns of the photomasks of the second andthird comparative examples, wherein the width L is varied continuously;

FIG. 6 is a plot of the simulation result at various wavelengths λ andnumerical apertures NA, wherein the maximum width L causing a phaseshifter to have a greater light-shielding effect than that of alight-shielding film is plotted with respect to λ/NA;

FIG. 7 is a plot of the simulation result at various wavelengths λ andnumerical apertures NA, wherein the width L maximizing thelight-shielding effect of the phase shifter is plotted with respect toλ/NA;

FIG. 8(a) is a plan view of a photomask of the first embodiment of theinvention, FIGS. 8(b) to (d) are diagrams showing the simulation resultof light intensity distribution of the light transmitted between twopoints A and B of the mask of FIG. 8(a), using the width L of 0.10 μm,0.14 μm and 0.18 μm, respectively, and various widths W, and FIG. 8(e)is a diagram showing the simulation result of a change in lightintensity of the light transmitted through the center of alight-shielding pattern on the mask of FIG. 8(a), using various widths Land various widths W;

FIG. 9 is a plot of the simulation result, wherein the maximum width Wcausing a mask enhancer to have a greater light-shielding effect thanthat of a light-shielding film is plotted with respect to the width L;

FIG. 10 is a plot of the simulation result, wherein the width Wmaximizing the light-shielding effect of the mask enhancer is plottedwith respect to the width L;

FIG. 11(a) is a plan view of a mask having a mask enhancer displacedfrom the center of a light-shielding pattern, and FIG. 11(b) is adiagram showing the simulation result of light intensity distribution ofthe light transmitted between two points A and B of the mask of FIG.11(a), wherein the offset width of the mask enhancer was varied;

FIGS. 12(a) to (c) are diagrams respectively showing the simulationresult of light intensity distribution obtained by a photomask of afourth comparative example, a photomask of a fifth comparative exampleand a photomask of the first embodiment of the invention including anoptimized mask enhancer, wherein the width of a light-shielding patternwas varied, and FIGS. 12(d) to (f) are diagrams respectively showing thesimulation result of light intensity distribution obtained by combiningeach of the photomasks of the fourth and fifth comparative examples andthe photomask of the first embodiment of the invention including theoptimized mask enhancer with annular exposure, wherein the width of thelight-shielding pattern was varied;

FIG. 13 is a diagram showing a light-source feature of the annularexposure;

FIG. 14(a) is a graphic representation of W=L and W=α×(A−L)/2 (whereA=0.8×λ/NA, and α=0.5, 1.0, 1.5 and 2.0), and FIG. 14(b) is a graphicrepresentation of W=L−2E and W=α×(A−L)/2 (where A=0.8×λ/NA, and α=0.5,1.0, 1.5 and 2.0);

FIG. 15 is a diagram showing the simulation result of a change in thelight-shielding effect obtained while varying the transmittance andphase of a phase shift region serving as a mask enhancer in thephotomask of the first embodiment of the invention;

FIGS. 16(a) to (e) are cross-sectional views illustrating the steps of apatterning method of a second embodiment of the invention, respectively;

FIGS. 17(a) to (c) are diagrams showing light-source features of normalexposure, annular exposure and quadrupole exposure, respectively;

FIG. 18(a) is a diagram showing the simulation result of the DOF valueupon normal exposure with the photomask of the first embodiment of theinvention, FIG. 18(b) is a diagram showing the simulation result of theDOF value upon annular exposure with the photomask of the firstembodiment of the invention, and FIG. 18(c) is a diagram showing thesimulation result of the DOF value upon quadrupole exposure with thephotomask of the first embodiment of the invention;

FIGS. 19(a) to (g) are cross-sectional views illustrating the steps of aphotomask producing method of a third embodiment of the invention,respectively, and FIGS. 19(h) to (l) are plan views corresponding toFIGS. 19(b), (c), (e), (f) and (g), respectively;

FIG. 20(a) is a diagram showing the state where a defect causing nophase inversion is present within the mask enhancer of the photomask ofthe first embodiment of the invention, and FIGS. 20(b) to (d) arediagrams showing the simulation result of light intensity distributionof the light transmitted between two points A and B of the mask of FIG.20(a), wherein the width L was 0.10 μm, 0.14 μm and 0.18 μm,respectively;

FIG. 21(a) is a diagram showing the state where an etching residue ofthe light-shielding film is left within the mask enhancer of thephotomask of the first embodiment of the invention, and FIGS. 21(b) to(d) are diagrams showing the simulation result of light intensitydistribution of the light transmitted between two points A and B of themask of FIG. 21(a), wherein the width L was 0.10 μm, 0.14 μm and 0.18μm, respectively;

FIGS. 22(a) to (g) are cross-sectional views illustrating the steps of aphotomask producing method of a first modification of the thirdembodiment of the invention, respectively, and FIGS. 22(h) to (k) areplan views corresponding to FIGS. 22(b), (c), (f) and (g), respectively;

FIGS. 23(a) to (h) are cross-sectional views illustrating the steps of aphotomask producing method of a second modification of the thirdembodiment of the invention, respectively, and FIGS. 23(i) to (m) areplan views corresponding to FIGS. 23(b), (c), (f), (g) and (h),respectively;

FIGS. 24(a) to (g) are cross-sectional views illustrating the steps of aphotomask producing method of a fourth embodiment of the invention,respectively, and FIGS. 24(h) to (l) are plan views corresponding toFIGS. 24(b), (c), (e), (f) and (g), respectively;

FIGS. 25(a) to (h) are cross-sectional views illustrating the steps of aphotomask producing method of a first modification of the fourthembodiment of the invention, respectively, and FIGS. 25(i) to (n) areplan views corresponding to FIGS. 25(b), (c), (d), (f), (g) and (h),respectively;

FIGS. 26(a) to (g) are cross-sectional views illustrating the steps of aphotomask producing method of a second modification of the fourthembodiment of the invention, respectively, and FIGS. 26(h) to (k) areplan views corresponding to FIGS. 26(b), (c), (e) and (g), respectively;

FIGS. 27(a) to (g) are cross-sectional views illustrating the steps of aphotomask producing method of a third modification of the fourthembodiment of the invention, respectively, and FIGS. 27(h) to (l) areplan views corresponding to FIGS. 27(b), (c), (d), (f) and (g),respectively;

FIGS. 28(a) to (g) are cross-sectional views illustrating the steps of aphotomask producing method of a fifth embodiment of the invention,respectively, and FIGS. 28(h) to (l) are plan views corresponding toFIGS. 28(b), (c), (e), (f) and (g), respectively;

FIGS. 29(a) to (g) are cross-sectional views illustrating the steps of aphotomask producing method of a modification of the fifth embodiment ofthe invention, respectively; and FIGS. 29(h) to (l) are plan viewscorresponding to FIGS. 29(b), (c), (e), (f) and (g), respectively;

FIG. 30 is a flowchart illustrating a pattern-layout producing methodand a mask-writing data producing method of a sixth embodiment of theinvention;

FIG. 31(a) is a diagram showing an example of pattern layout produced instep S1 of the pattern-layout producing method of the sixth embodimentof the invention, FIG. 31(b) is a diagram showing line patterns, patternend and pattern corner extracted from the pattern layout of (a) in stepS2 of the pattern-layout producing method of the sixth embodiment of theinvention, FIG. 31(c) is a diagram showing mask enhancers that areprovided inside the line patterns and the like of FIG. 31(b) in step S3of the pattern-layout producing method of the sixth embodiment of theinvention, FIG. 31(d) is a diagram showing the pattern layout in whichthe mask enhancers are arranged with a dimension as determined based onthe dimension of the line patterns and the like shown in FIG. 31(c) instep S4 of the pattern-layout producing method of the sixth embodimentof the invention, FIG. 31(e) is a diagram showing the pattern layoutafter dimensional adjustment of the mask enhancers of FIG. 31(d) in stepS5 of the mask-writing data producing method of the sixth embodiment ofthe invention, FIG. 31(f) is a diagram showing the mask-patternformation data determined based on the dimensionally adjusted patternlayout of FIG. 31(e) in step S6 of the mask-writing data producingmethod of the sixth embodiment of the invention, and FIG. 31(g) showsthe mask-enhancer formation data determined based on the dimensionallyadjusted pattern layout of FIG. 31(e) in step S6 of the mask-writingdata producing method of the sixth embodiment of the invention;

FIG. 32(a) is a diagram showing an example of a pattern whose minimumdimension is sufficiently larger than the resolution, and FIG. 32(b) isa diagram showing the simulation result of light intensity distributionprojected upon forming the pattern of FIG. 32(a) using a conventionalphotomask;

FIG. 33(a) is a diagram showing an example of a pattern whose minimumdimension corresponds to about the resolution, and FIG. 33(b) is adiagram showing the simulation result of light intensity distributionprojected upon forming the pattern of FIG. 33(a) using a conventionalphotomask;

FIG. 34(a) is a plan view of a first photomask used in a patterningmethod of a first conventional example, FIG. 34(b) is a cross-sectionalview taken along line I-I of FIG. 34(a), FIG. 34(c) is a plan view of asecond photomask used in the patterning method of the first conventionalexample, and FIG. 34(d) is a diagram showing a resist pattern formed bythe patterning method using the first and second photomasks of FIGS.34(a) and 34(c); and

FIG. 35 is a plan view of a photomask used in a patterning method of asecond conventional example.

BEST MODE FOR CARRYING OUT THE INVENTION FIRST EMBODIMENT

Hereinafter, a photomask according to the first embodiment of theinvention will be described with reference to the figures. Note that, inthe first embodiment, NA indicates a numerical aperture (e.g., 0.6) of areduction projection optical system of an aligner, λ indicates awavelength (e.g., 0.193 μm) of exposure light, i.e., a light source, andM indicates a magnification (e.g., 4 or 5) of the reduction projectionoptical system of the aligner.

FIG. 1 shows the basic structure of the photomask according to the firstembodiment.

As shown in FIG. 1, a light-shielding film region 101 of alight-shielding film is formed on a transparent substrate 100, and aphase shift region 102 is provided inside the light-shielding filmregion 101. The width of the light-shielding film region 101 includingthe phase shift region 102 is L×M, the width of the phase shift region102 is W×M, and the width of the portion of the light-shielding filmregion 101 surrounding the phase shift region 102 is S×M. The phaseshift region 102 is formed as follows: for example, an opening havingthe same contour as that of the phase shift region 102 is formed in thelight-shielding film of the light-shielding film region 101, and thetransparent substrate 100 located under the opening is removed down tosuch a depth that produces an optical path difference corresponding tohalf the wavelength (converted based on the wavelength λ) of thetransmitted light. Thus, light transmitted through the phase shiftregion 102 has a phase difference of about 180 degrees from the lighttransmitted through the light-transmitting region (the portion includingneither the light-shielding film region 101 nor the phase shift region102) of the transparent substrate 100.

The first embodiment is characterized in that a light-shielding patternis formed from the light-shielding film region 101 and the phase-shiftregion 102. In other words, by using, e.g., the photomask of FIG. 1, apattern having a width L can be formed on the wafer. For example, it isnow assumed that the dimension of a desired pattern (or a design value)on the wafer is 0.1 μm, L=0.1 μm. When an aligner with magnification M=4is used, the dimension of the light-shielding pattern on the photomaskis M×L=0.1×4=0.4 μM.

FIG. 2 is a plan view of a desired design pattern to be formed on thesubstrate to be exposed. —FIG. 3(a) is a plan view of a photomask of afirst comparative example for forming the pattern of FIG. 2.

As shown in FIG. 3(a), in the photomask of the first comparativeexample, a light-shielding pattern 111 formed only from alight-shielding film such as a chromium film is formed on a transparentsubstrate 110 of a material that is highly transparent to an exposurelight source, such as glass. The light-shielding pattern 111 has thedimension of a desired pattern (normally, a design value) multiplied byM. For example, when the outer width of the desired pattern is 1 μm, theouter width of the light-shielding pattern 111 is M μm. Note that, aregion 110 a located outside the light-shielding pattern 111 in thetransparent substrate 110 serves as a light-transmitting region. As theexposure light source, i-line (365 nm), KrF excimer laser light (248mm), ArF excimer laser light (193 nm), or F2 excimer laser light (157nm) or the like can be used.

FIG. 3(b) shows the simulation result of light intensity distributionprojected to a resist film when the resist film is subjected to exposureusing the photomask of FIG. 3(a). Note that the simulation of lightintensity distribution was conducted under the following opticalconditions: wavelength λ=0.193 μm; numerical aperture NA=0.6; andcoherence σ=0.8. FIG. 3(b) shows the light intensity distribution usingcontour lines of the relative light intensity in a two-dimensionalrelative coordinate system.

When the photomask of FIG. 3(a) is used, light reaches the backside ofthe light-shielding film of the light-shielding pattern 111 at locationssuch as a portion having a narrow line width (e.g., region R1), a lineend (e.g., region R2) or a pattern corner (corner; e.g., region R3), dueto the diffraction phenomenon. Accordingly, the exposure light cannotsufficiently be shielded using the light-shielding pattern 111 as amask. As a result, as shown in FIG. 3(b), the light intensitydistribution is significantly deformed from the profile similar to thefeature of the light-shielding pattern 111, i.e., desired pattern.Moreover, in a region where a pattern having a line width equal to orsmaller than about the resolution determined by the aforementionedoptical conditions, specifically, a line width of about 0.13 μm or less,is to be formed (e.g., region R11 or R2′), the light intensitydistribution has an increased distance between contour lines of therelative light intensity. As a result, variation in pattern dimensionresulting from variation in exposure energy is increased. Thus, anexposure margin of the resist film is reduced, making it extremelydifficult to obtain a stable pattern feature.

FIG. 3(c) shows the comparison result between the desired patternfeature and the profile of a contour line of the relative lightintensity of FIG. 3(b), i.e., a contour line that is considered torepresent the resist pattern feature produced by development of theresist film.

As shown in FIG. 3(c), in the expected resist pattern feature, a lineend (e.g., region R2′) or a pattern corner (e.g., region R3′) iswithdrawn from the desired pattern feature, and a portion having a linewidth of about 0.13 μm (resolution) or less (e.g., region R1′) isnarrower than the desired pattern feature.

Therefore, the inventor produced a photomask of the first embodiment,i.e., a photomask having a phase shift region within a light-shieldingpattern, for example, inside a portion of the light-shielding patternhaving a line width of about (M×resolution) or less, at a line end, orat a pattern corner. These phase shift regions provide the lighttransmitted therethrough with a phase difference of about 180 degreeswith respect to the light transmitted through a normallight-transmitting region.

FIG. 4(a) is a plan view of the photomask of the first embodiment forforming the pattern of FIG. 2.

As shown in FIG. 4(a), in the photomask of the first embodiment, alight-shielding film region 121 formed from a light-shielding film suchas a chromium film is formed on a transparent substrate 120. The outerdimension of the light-shielding film region 121 corresponds to thedimension of a desired pattern multiplied by M. For example, when theouter width of the desired pattern is 1 μm, the outer width of thelight-shielding film region 121 is M μm. Note that, a region 120 alocated outside the light-shielding film region 121 in the transparentsubstrate 120 serves as a light-transmitting region. Moreover, phaseshift regions 122 are formed inside the light-shielding region 121. Thephase shift regions 122 provide the light transmitted therethrough witha phase difference of about 180 degrees from the light transmittedthrough the light-transmitting region 120 a and have an approximatelyequivalent transmittance to that of the light-transmitting region 120 a.Moreover, a light-shielding pattern is formed from the light-shieldingfilm region 121 and the phase shift regions 122.

More specifically, the phase shift regions 122 are provided in thelight-shielding pattern at locations such as inside a portion having aline width of about M×0.13 μm (resolution) or less (e.g., region r1), ata line end (e.g., region r2) or at a pattern corner (e.g., region r3).The phase shift region 122 is formed as follows: for example, an openinghaving the same contour as that of the phase shift region 122 is formedin the light-shielding film of the light-shielding film region 121, andthe transparent substrate 120 located under the opening is removed downto such a depth that produces an optical path difference correspondingto half the wavelength (converted based on the wavelength λ) of thetransmitted light.

FIG. 4(b) shows the simulation result of light intensity distributionprojected to a resist film when the resist film is subjected to exposureusing the photomask of FIG. 4(a). Note that the simulation of lightintensity distribution was conducted under the following opticalconditions: wavelength λ=0.193 μm; numerical aperture NA=0.6; andcoherence σ=0.8. FIG. 4(b) shows the light intensity distribution usingcontour lines of the relative light intensity in a two-dimensionalrelative coordinate system.

As shown in FIG. 4(b), the light intensity distribution obtained by thephotomask of FIG. 4(a) has a profile similar to the feature of alight-shielding pattern formed from the light-shielding film region 121and the phase shift regions 122, i.e., a desired pattern. As a whole,the light intensity distribution has a small distance between contourlines of the relative light intensity. As a result, variation in patterndimension resulting from variation in exposure energy is reduced. Thus,an exposure margin of the resist film is increased, thereby facilitatingformation of a stable pattern feature.

FIG. 4(c) shows the comparison result between the desired patternfeature and the profile of a contour line of the relative lightintensity of FIG. 4(b), i.e., a contour line that is considered torepresent the resist pattern feature produced by development of theresist film.

As shown in FIG. 4(c), in the expected resist pattern feature, a lineend (e.g., region r2′) or a pattern corner (e.g., region r3′) is notwithdrawn from the desired pattern feature, or a portion having a linewidth of about 0.13 μm (resolution) or less (e.g., region r1′) does notbecome narrower than the desired pattern feature, as opposed to the casewhere the photomask of the first comparative example is used. In otherwords, the use of the photomask of the first embodiment enablesformation of a desired pattern feature.

From the aforementioned results, the inventor found the principle thatthe phase shift region exhibits a better light-shielding property thanthat of the light-shielding film region when the light-transmittingregion and the phase shift region having a phase difference of 180degrees with respect to the light-transmitting region are arranged onthe photomask so as to satisfy prescribed conditions.

In order to specify the prescribed conditions, the light-shieldingproperty of the structure using only the light-shielding film or phaseshifter as a light-shielding pattern will now be described withreference to the figures.

FIG. 5(a) is a plan view of a mask with a light-shielding pattern formedon a transparent substrate, wherein the light-shielding pattern isformed only from a light-shielding film (hereinafter, this mask isreferred to as a photomask of the second comparative example). As shownin FIG. 5(a), an isolated line pattern 131 having a width of (L×M) isformed from a light-shielding film such as a chromium film on atransparent substrate 130.

FIG. 5(b) is a plan view of a mask with a light-shielding pattern formedon a transparent substrate, wherein the light-shielding pattern isformed only from a phase shifter (hereinafter, this mask is referred toas a photomask of the third comparative example). As shown in FIG. 5(b),an isolated line pattern 141 having a width of (L×M) is formed from aphase shifter on a transparent substrate 140.

FIGS. 5(c) to (e) show the simulation result of light intensity(relative light intensity) distribution of the light transmitted betweentwo points A and B of the photomasks of the second and third comparativeexamples, wherein the width L was 0.06 μm, 0.10 μm and 0.16 μm,respectively (optical conditions: wavelength λ=0.193 μm; numericalaperture NA=0.6; and coherence σ=0.8). Note that, in FIGS. 5(c) to (e),the dotted line indicates the light intensity distribution of the lighttransmitted between two points A and B of the photomask of the secondcomparative example, and the solid line indicates the light intensitydistribution of the light transmitted between two points A and B of thephotomask of the third comparative example. In FIGS. 5(c) to (e), it canbe determined that each mask has a greater light-shielding effect as thelight intensity at the origin of the abscissa, i.e., in the center ofthe isolated line pattern 131 or isolated line pattern 141 is lower.

FIG. 5(f) shows the simulation result of a change in light intensity(relative light intensity) of the light transmitted through the centerof the isolated line pattern 131 (the photomask of the secondcomparative example) and the isolated line pattern 141 (the photomask ofthe third comparative example), wherein the width L was variedcontinuously (optical conditions: wavelength λ=0.193 μm; numericalaperture NA=0.6; and coherence σ=0.8). Note that, in FIG. 5(f), thedotted line indicates a change in light intensity of the lighttransmitted through the center of the isolated line pattern 131, and thesolid line indicates a change in light intensity of the lighttransmitted through the center of the isolated line pattern 141.

As shown in FIGS. 5(c) to (e) and FIG. 5(f), when the width L is smallerthan about the resolution, i.e., about 0.13 μm, the phase shifter has agreater light-shielding effect than that of the light-shielding film.However, when the width L exceeds about 0.13 μm, the phase shifter has apoorer light-shielding effect than that of the light-shielding film. Inother words, the maximum width L causing the phase shifter to have agreater light-shielding effect than that of the light-shielding film isabout 0.13 μm.

As shown in FIG. 5(f), the maximum light-shielding effect of the phaseshifter is obtained with the width of around 0.10 μm.

FIG. 6 shows the simulation result at various wavelengths λ andnumerical apertures NA, wherein the maximum width L causing the phaseshifter to have a greater light-shielding effect than that of thelight-shielding film (chromium film) is plotted with respect to λ/NA.

As shown in FIG. 6, the approximate relation as given by L=0.4×λ/NA isestablished between λ/NA and the maximum width L causing the phaseshifter to have a greater light-shielding effect than that of thelight-shielding film. In other words, when the isolated line pattern ofthe phase shifter formed on the transparent substrate has a width (L×M)equal to or smaller than (0.4×λ/NA)×M, this isolated line pattern has agreater light-shielding effect than that of the isolated line pattern ofthe light-shielding film.

FIG. 7 shows the simulation result at various wavelengths λ andnumerical apertures NA, wherein the width L maximizing thelight-shielding effect of the phase shifter is plotted with respect toλ/NA.

As shown in FIG. 7, the approximate relation as given by L=(0.8/3)×λ/NAis established between λ/NA and the width L maximizing thelight-shielding effect of the phase shifter. In other words, when theisolated line pattern of the phase shifter formed on the transparentsubstrate has a width (L×M) of about (0.8/3)×λ/NA)×M, this isolated linepattern has the maximum light-shielding effect.

From the aforementioned results, the inventor found that alight-shielding pattern having an excellent light-shielding property canbe implemented by the structure having a phase shifter of a prescribeddimension or less surrounded by a light-shielding film, i.e., thestructure having a phase shift region surrounded by a light-shieldingfilm region.

In order to specify the conditions capable of enhancing thelight-shielding property of the light-shielding film by the phaseshifter, the light-shielding property of a light-shielding patternformed from combination of a phase shift region and a light-shieldingfilm region will now be described with reference to the figures.

FIG. 8(a) is a plan view of a mask having a light-shielding patternformed from combination of a phase-shift region and a light-shieldingfilm region, i.e., a photomask of the first embodiment. As shown in FIG.8(a), a light-shielding film region 151 is formed on a transparentsubstrate 150 so as to surround a phase shift region 152, and thelight-shielding pattern is formed from the light-shielding film region151 and the phase-shift region 152. The width of the light-shieldingfilm region 151 including the phase shift region 152 is (L×M), the widthof the phase shift region 152 is (W×M), and the width of the portionsurrounding the phase shift region 152 in the light-shielding filmregion 151 is (S×M). Thus, L=W+2S.

FIGS. 8(b) to (d) show the simulation result of light intensity(relative light intensity) distribution of the light transmitted betweentwo points A and B of the mask of FIG. 8(a), using the width L of 0.10μm, 0.14 μm and 0.18 μm, respectively, and various widths W (opticalconditions: wavelength λ=0.193 μm; numerical aperture NA=0.6; andcoherence σ=0.8).

FIG. 8(e) shows the simulation result of a change in light intensity(relative light intensity) of the light transmitted through the centerof the light-shielding pattern on the mask of FIG. 8(a), using variouswidths L and various widths W (optical conditions: wavelength λ=0.193μm; numerical aperture NA=0.6; and coherence σ=0.8).

FIG. 9 shows the simulation result obtained based on FIGS. 8(b) to (d)and FIG. 8(e), wherein the maximum width W causing the structure formedfrom combination of the phase shift region and the light-shielding filmregion to have a greater light-shielding effect (lower light intensity)than that of the structure formed only from the light-shielding film(chromium film) (corresponding to W=0) is plotted with respect to thewidth L.

According to the aforementioned property of the light-shielding effectresulting only from the phase shifter, it is expected that, providedthat the phase shifter is provided inside the light-shielding film so asto be surrounded by the light-transmitting region (the region of thetransparent substrate having no light-shielding pattern) at a distanceof 0.4×λ/NA or less, that is, so as to satisfy W+S·0.4×λ/NA, thislight-shielding pattern would implement a greater light-shielding effectthan that of a light-shielding pattern having the same dimension butformed only from the light-shielding film. Note that, when W+S·0.4×λ/NAis satisfied, L·(0.8×λ/NA)−W. Therefore, L·(0.8×λ/NA) is satisfied.

On the other hand, as shown in FIG. 9, the approximate relation as givenby W=(0.8×λ/NA)−L is established between the width L and the maximumwidth W causing the structure formed from combination of the phase shiftregion and the light-shielding film region to have a greaterlight-shielding effect than that of the structure using only thelight-shielding film. In other words, it is assumed that an openinghaving a width of (W×M) is formed inside a light-shielding film having awidth of (L×M) for use as a phase shift region. In this case, as long asW·(0.8×λ/NA)−L is satisfied, the light-shielding effect can be improvedover the case where the light-shielding film having a width of (L×M) isdirectly used. Note that, when W·(0.8×λ/NA)−L is satisfied,W+S·0.4×λ/NA. Therefore, the result of FIG. 9 corresponds to theexpectation described above. Provided that L·0.4×λ/NA, even thelight-shielding pattern formed only from the phase shifter, i.e., W=L,can improve the light-shielding effect over the light-shielding patternformed only from the light-shielding film.

From the aforementioned results, the inventor found that thelight-shielding effect of a light-shielding pattern having a width (L×M)of (0.8×λ/NA)×M or less is improved by forming therein a phase shiftregion, i.e., an opening, having a width (W×M) of ((0.8×λ/NA)−L)×M orless. Hereinafter, a phase shift region formed inside a light-shieldingpattern so as to satisfy the aforementioned conditions is referred to asa mask enhancer.

FIG. 10 shows the simulation result obtained based on FIGS. 8(b) to (d)and FIG. 8(e), wherein the width W maximizing the light-shielding effectof the mask enhancer is plotted with respect to the width L.

As shown in FIG. 10, the approximate relation as given byW=((0.8×λ/NA)−L)/2 is established between the width L and the width Wmaximizing the light-shielding effect of the mask enhancer. In otherwords, it is assumed that an opening having a width of (W×M) is formedwithin a light-shielding film having a width of (L×M) for use as a maskenhancer. In this case, when W=((0.8×λ/NA)−L)/2, the mask enhancer hasthe maximum light-shielding effect.

The inventor also found that, provided that a light-shielding patternformed from a light-shielding film and a mask enhancer located thereinhas a width of (L×M) and the mask enhancer has a width of (W×M) as wellas W·(0.8×λ/NA)−L, the mask enhancer improves the light-shielding effecteven if the mask enhancer is not located in the center of thelight-shielding pattern.

FIG. 11(a) is a plan view of a mask having a mask enhancer displacedfrom the center of a light-shielding pattern. As shown in FIG. 11(a), alight-shielding film region 161 is formed on a transparent substrate 160so as to surround a mask enhancer 162. The light-shielding pattern isformed from the light-shielding film region 161 and the mask enhancer162. The width of the light-shielding film region 161 including the maskenhancer 162, i.e., the width of the light-shielding pattern, is (L×M),the width of the mask enhancer 162 is (W×M), and the offset widthbetween the respective center lines of the light-shielding pattern andthe mask enhancer 162 is (d×M).

FIG. 11(b) shows the simulation result of light intensity (relativelight intensity) distribution of the light transmitted between twopoints A and B of the mask of FIG. 11(a), wherein the width L was 0.14μm, the width W was 0.06 μm, and the offset width d was varied in therange of −0.03 μm to 0.03 μm (optical conditions: wavelength λ=0.193 μm;numerical aperture NA=0.6; and coherence σ=0.8).

As shown in FIG. 11(b), the mask enhancer has substantially the samelight-shielding effect regardless of its position on the light-shieldingpattern. Although the displacement amount of the mask enhancer is 0.06μm×M (which is the displacement amount between d=−0.03 μm and d=0.03μm), the displacement amount of the light intensity distribution itselfis about 0.02 μm. Thus, displacement of the mask enhancer has a slighteffect on the light intensity distribution. Accordingly, it can beappreciated that the positional control of the mask enhancer is not soimportant in the light-shielding pattern structure using the maskenhancer.

As has been described above, according to the first embodiment, a maskenhancer having a width (W×M) of ((0.8×λ/NA)−L)×M or less is providedinside a light-shielding pattern having a width (L×M) of (0.8×λ/NA)×M orless. Therefore, the transmitted light reaching the backside of thelight-shielding film region of the light-shielding pattern due to thediffraction phenomenon is cancelled by the light transmitted through themask enhancer. As a result, the light-shielding effect of thelight-shielding pattern is improved. In this case, by providing the maskenhancer so as to satisfy W=((0.8×λ/NA)−L)/2, the light-shielding effectof the light-shielding pattern can be maximized. Provided thatL·0.4×λ/NA, even the light-shielding pattern formed only from the phaseshifter, i.e., W=L, can improve the light-shielding effect over thelight-shielding pattern formed only from the light-shielding film.

Hereinafter, the light-shielding property obtained by the mask enhancerwith an optimized width will be described with reference to the figures.

FIGS. 12(a) to (c) show the simulation result of light intensitydistribution obtained by the following masks: a simple light-shieldingfilm mask whose light-shielding pattern is formed only from alight-shielding film (hereinafter, referred to as a photomask of thefourth comparative example); a halftone phase shit mask (hereinafter,referred to as a photomask of the fifth comparative example); and a maskof the present embodiment including a mask enhancer with an optimizedwidth in the light-shielding pattern, wherein the light-shieldingpattern has a width of (L×M) and L was varied in the range of 0.26 μm to0.10 μm.

FIGS. 12(d) to (f) show the simulation result of light intensitydistribution obtained by combination of the photomasks of the fourth andfifth comparative examples and the present embodiment with annularexposure as shown in FIG. 13 (a light-shielding filter having a radiusequal to two-thirds of the radius of the light source is provided in thecenter of the light source of the aligner), wherein the light-shieldingpattern has a width of (L×M) and L is varied in the range of 0.26 μm to0.10 μm.

Note that the simulation of light intensity distribution of FIGS. 12(a)to (f) was conducted under the following optical conditions: wavelengthλ=0.193 μm; numerical aperture NA=0.6; and coherence σ=0.8, and thus0.8×λ/NA≈0.26 μm and (0.8/3)×λ/NA 0.09 μm. The light intensitydistribution shown in FIGS. 12(a) to (f) is calculated along thetransverse direction of the light-shielding pattern using the center ofthe light-shielding pattern as the origin.

As shown in FIG. 12(a), in the case of the simple light-shielding filmmask, the light-shielding effect of the light-shielding pattern isdegraded as L becomes smaller than 0.8×λ/NA (0.26 μm), whereby anexposure margin is abruptly reduced.

As shown in FIG. 12(b), in the case of the halftone phase shift mask aswell, the light-shielding effect of the light-shielding pattern isdegraded as L becomes smaller, whereby an exposure margin is abruptlyreduced.

As shown in FIG. 12(c), in the case of the mask of the presentembodiment having the optimized mask enhancer structure, approximatelythe same light-shielding effect is obtained with any width L in therange of 0.8×λ/NA to (0.8/3)×λ/NA (about 0.10 μm). Note that, asdescribed before, when L is 0.8×λ/NA or more, a sufficientlight-shielding effect is obtained by a normal light-shielding patternformed only from the light-shielding film. Therefore, with the maskenhancer structure, a sufficient light-shielding effect can be realizedwith any width L of (0.8/3)×λ/NA or more. It is clearly understood that,in the present embodiment, L=(0.8/3)×λ/NA does not mean the resolutionlimit, and a pattern can be formed with the mask enhancer even if L is(0.8/3)×λ/NA or less.

As shown in FIGS. 12(a) and 12(d) or FIGS. 12(b) and 12(e), the simplelight-shielding film mask or the halftone phase shift mask has adegraded light-shielding property when combined with annular exposure.In contrast, as shown in FIGS. 12(c) and 12(f), the mask of the presentembodiment does not have a degraded light-shielding property even incombination with annular exposure.

Note that the effects resulting from combining the mask of the presentembodiment with annular exposure will be described later.

Hereinafter, the relation between L and W will be described withreference to the figures. It is herein assumed that the width of thelight-shielding pattern including the mask enhancer is (L×M) and thewidth of the mask enhancer is (W×M).

FIG. 14(a) is a graphic representation of W=L and W=α×(A−L)/2 (whereA=0.8×λ/NA, and α=0.5, 1.0, 1.5 and 2.0), wherein the abscissa is L andthe ordinate is W. Herein, W=α×(A−L)/2 satisfies the condition relatingto the width (W×M) of the mask enhancer: W·(0.8×λ/NA)−L=A−L (where W·L).Disregarding the minimum possible dimension to be implemented on thephotomask, W·L for the width (W×M) of the mask enhancer.

In FIG. 14(a), the intersection of W=L and W=α×(A−L)/2 is marked with“•” and the value L at the intersection is α×A/(2+α).

As described before, the mask enhancer is provided in thelight-shielding pattern satisfying L<A. As shown in FIG. 14(a), whenL<A, the value W=α×(A−L)/2 is increased as L is decreased, and becomesequal to L at the point “•”. Thus, when L is smaller than this value,the light-shielding pattern can be formed only from the phase shifter.For example, when α=1, the light-shielding pattern of L<A/3 may beformed only from the phase shifter.

FIG. 14(b) is a graphic representation of W=L−2E and W=α×(A−L)/2 (whereA=0.8×λ/NA, and α=0.5, 1.0, 1.5 and 2.0), wherein the abscissa is L andthe ordinate is W. Herein, (E×M) is the minimum possible dimension to beimplemented on the photomask, and for example, means a valueapproximately corresponding to the alignment accuracy of a photomaskwriting apparatus. It should be understood that the width (L×M) of thelight-shielding pattern including the mask enhancer and the width (W×M)of the mask enhancer are both equal to or larger than the minimumpossible dimension (E×M). Since the light-shielding film having a widthof at least (E×M) must be left on both sides of the mask enhancer,W·L−2E for the width (W×M) of the mask enhancer.

In FIG. 14(b), the intersection of W=L−2E and W=α×(A=L)/2 is marked with“•”, and the value L at the intersection is (α×A+4×E)/(2+α).

As shown in FIG. 14(b), when L<A, the value w=α×(A−L)/2 is increased asL is decreased, and becomes equal to L−2E at the point “•”, as in thecase of FIG. 14(a). Thus, when L is smaller than this value, only thewidth of the mask enhancer is reduced. That is, only the width of themask enhancer is reduced as L is decreased, so that the light-shieldingfilm of the width (E×M) is left on both sides of the mask enhancer. Forexample, when α=1, only the width of the mask enhancer is varied in thelight-shielding pattern of L<(A+4×E)/3.

AS shown in FIG. 14(a) and FIG. 14(b), if the width (W×M) of the maskenhancer is determined within the range of W·2×(A−L)/2=A−L and W·L orW·L−2E, the light-shielding property can be improved by the maskenhancer. The light-shielding property of the mask enhancer is maximizedwhen both W=(A−L)/2 and L·A/3 are satisfied. However, thelight-shielding property can be sufficiently improved by the maskenhancer as long as 0.5×(A−L)/2·W·1.5×(A−L)/2 and W·L or W·L−2E aresatisfied.

Hereinafter, the relation between the transmittance and phase of themask enhancer and the light-shielding effect thereof will be described.

FIG. 15 shows the simulation result of a change in the light-shieldingeffect in the mask of the present embodiment having a mask enhancer witha width optimized at L=0.10 μm, wherein the width of the light-shieldingpattern is (L×M), that is, the simulation result of a change in thelight-shielding effect obtained while varying the transmittance andphase of a phase shift region serving as mask enhancer. Note that thelight-shielding effect was evaluated by the following expression: (F(X,Y)−F(180, 1.0))/F(180, 1.0) (where X is a phase, Y is transmittanceintensity (the square of phase transmittance; the transmittanceintensity of the light-transmitting region is 1), and F(X, Y) is thelight intensity at the center of the light-shielding pattern). In FIG.15, the transmittance and phase values are plotted for the evaluationexpressions of the light-shielding effect of 1.0, 2.0 and 3.0.

Provided that the condition where the evaluation expression of thelight-shielding effect becomes equal to 1, i.e., the condition where achange in light intensity becomes equal to the minimum light intensityF(180, 1.0) according to a change in transmittance and phase, is theallowable limit of the light-shielding effect of the mask enhancer, thephase difference of the mask enhancer with respect to thelight-transmitting region is preferably in the range of (170+360×n) to(190+360×n) degrees (where n is an integer), as shown in FIG. 15. Thetransmittance intensity of the mask enhancer is preferably 80% or moreof the transmittance intensity of the light-transmitting region.

Note that the foregoing description is given assuming that thelight-shielding pattern is a line pattern. However, the mask enhancerhas the effect of improving the light-shielding property when it isprovided inside the light-shielding film so as to be surrounded by thelight-transmitting region from at least two directions at a distance of0.4×λ/NA or less. Accordingly, the mask enhancer improves thelight-shielding effect even when it is provided at or inside a corner ofthe light-shielding pattern, or at or inside an end of thelight-shielding pattern formed as a line pattern. This enables formationof a fine pattern with a feature truly similar to that of a desiredlight-shielding pattern.

SECOND EMBODIMENT

Hereinafter, a patterning method according to the second embodiment ofthe invention will be described with reference to the figures. Note thatthe patterning method of the second embodiment is a patterning methodusing the photomask of the first embodiment. In the second embodiment, Mindicates a magnification of a reduction projection optical system of analigner.

FIGS. 16(a) to (e) are cross-sectional views illustrating the steps ofthe patterning method of the second embodiment, respectively.

First, as shown in FIG. 16(a), a film 201 to be etched of a metal filmor insulating film is formed on a substrate 200. An underlyinginsulating film, underlying wirings, active elements such astransistors, or the like may be formed in advance on the substrate 200.

Then, as shown in FIG. 16(b), a resist film 202 is formed on the etchingfilm 201.

Note that the present embodiment uses a positive resist, a resist whoseexposed portion is removed by development, as a material of the resistfilm 202. However, a negative resist may alternatively be used in orderto form a fine resist-removed region like a hole pattern.

Then, as shown in FIG. 16(c), the resist film 202 is subjected topattern exposure using the photomask of the first embodiment, i.e., aphotomask 203 having a light-shielding pattern 203 a of the maskenhancer structure. More specifically, exposure light 204 is directed tothe photomask 203, so that the light 205 transmitted therethrough isincident on a prescribed portion of the resist film 202.

Then, as shown in FIG. 16(d), the exposed resist film 202 is developedto form a resist pattern 202A.

Thereafter, as shown in FIG. 16(e), the etching film 201 is etched usingthe resist pattern 202A as an etching mask, thereby forming a pattern201A of the etching film 201.

According to the second embodiment, pattern exposure is conducted usingthe photomask of the first embodiment. Therefore, even when the resistpattern 202A or pattern 201A having a dimension equal to or smaller thanabout the resolution is formed, the light-shielding pattern 203 aprovides approximately the same light-shielding effect as that providedwhen a pattern having a dimension equal to or larger than about theresolution is formed. Accordingly, the resist pattern 202A or pattern201A having any feature and any dimension including a dimension equal toor smaller than about the resolution can be formed by exposure usingonly the photomask of the first embodiment.

The inventor found that, in addition to the improved light-shieldingproperty, a unique effect, i.e., an improved process margin such asfocus characteristics, can be obtained by the use of the mask enhancer.Hereinafter, this effect of improved process margin will be describedwith reference to the figures.

FIGS. 17(a) to (c) shows light-source features of normal exposure,annular exposure and quadrupole exposure, respectively. The annularexposure and quadrupole exposure are examples of oblique-incidenceexposure.

FIG. 18(a) shows the simulation result of the DOF (Depth of Focus)values of the following three photomasks upon normal exposure of FIG.17(a): a simple light-shielding film mask (the photomask of the fourthcomparative example); a halftone phase shift mask (the photomask of thefifth comparative example); and a photomask of the first embodimenthaving the mask enhancer with optimized width (hereinafter, referred toas the photomask of the invention), wherein the light-shielding patternhas a width (L×M) and L was varied in the range from 0.10 μm to 0.25 μm.

FIG. 18(b) shows the simulation result of the DOF values of thephotomasks of the fourth and fifth comparative examples and thephotomask of the invention upon annular exposure of FIG. 17(b), whereinthe light-shielding pattern has a width (L×M) and L was varied in therange from 0.05 μm to 0.25 μm.

FIG. 18(c) shows the simulation result of the DOF values of thephotomasks of the fourth and fifth comparative examples and thephotomask of the invention upon quadrupole exposure of FIG. 17(c),wherein the light-shielding pattern has a width (L×M) and L was variedin the range from 0.05 μm to 0.30 μm.

Note that, in FIGS. 18(a) to (c), a line width varying depending on afocus position (Critical Dimension; hereinafter, referred to as CD) wassimulated under the conditions to realize an arbitrary value L. Thus, anallowable range of the focus position in which the CD varies within ±10%of the CD value at the focus position=0 was obtained as a DOF value.

As shown in FIGS. 18(a) to (c), the halftone phase shift mask combinedwith an oblique incidence illumination method such as an annularillumination or quadrupole illumination method improves the DOF (overthe normal exposure) only to about the same degree as that of the simplelight-shielding film mask. In contrast, by using the oblique incidenceillumination method, the photomask of the invention having the maskenhancer structure significantly improves the DOF as L is decreased.

Thus, the mask enhancer has not only the effect of improving thelight-shielding property, but also the effect of improving a processmargin such as DOF when combined with the oblique-incidence illuminationmethod. In other words, the mask enhancer adjusted to maximize thelight-shielding effect has very good exposure-energy characteristics andfocus characteristics when combined with the oblique-incidenceillumination method. Accordingly, in order to form a pattern having anarbitrary dimension of 0.8×λ/NA or less, the mask enhancer is providedin the light-shielding pattern on the photomask, and oblique-incidenceexposure is conducted. As a result, a fine pattern that cannot beproduced with a conventional photomask can be realized as well as a highyield can be implemented in the LSI manufacturing with a high processmargin.

THIRD EMBODIMENT

Hereinafter, a method for producing a photomask according to the thirdembodiment of the invention will be described with reference to thefigures. Note that the photomask producing method of the thirdembodiment is a method for producing the photomask of the firstembodiment, i.e., a photomask including an isolated light-shieldingpattern formed from a light-shielding film region and a mask enhancer ona transparent substrate. In the third embodiment, NA is a numericalaperture of a reduction projection optical system of an aligner, λ is awavelength of exposure light, i.e., a light source, and M is amagnification of the reduction projection optical system of the aligner.

FIGS. 19(a) to (g) are cross-sectional views illustrating the steps ofthe photomask producing method of the third embodiment, respectively.FIGS. 19(h) to (l) are plan views corresponding to FIGS. 19(b), (c),(e), (f) and (g), respectively.

First, as shown in FIG. 19(a), a light-shielding film 301 of, e.g., achromium compound is deposited on a transparent substrate 300 of, e.g.,quartz glass. Then, a resist is applied to the light-shielding film 301to form a first resist film 302.

Then, a pattern is written on the first resist film 302 by using a maskwriting apparatus such as an electron-beam (EB) lithography system. Thefirst resist film 302 is then developed, whereby a first resist pattern302A covering a mask-pattern formation region is produced as shown inFIG. 19(b) or FIG. 19(h).

Thereafter, the light-shielding film 301 is etched using the firstresist pattern 302A as a mask. As a result, as shown in FIG. 19(c) orFIG. 19(i), a mask pattern 301A of the light-shielding film 301 isformed, and then the first resist pattern 302A is removed. If there areany defects in the mask pattern 301A after completion of the step ofFIG. 19(c), a repairing step or the like in the conventional maskmanufacturing method is conducted.

Then, as shown in FIG. 19(d), a resist is applied to the transparentsubstrate 300 with the mask pattern 301A so as to form a second resistfilm 303.

Thereafter, a pattern is written on the second resist film 303 by usingthe mask writing apparatus. The second resist film 303 is thendeveloped, whereby a second resist pattern 303A having an opening in themask-enhancer formation region is formed as shown in FIG. 19(e) or FIG.19(j). Note that the mask-enhancer formation region is always locatedinside the mask pattern 301A. Therefore, the opening of the secondresist pattern 303A is always formed on the mask pattern 301A.

As shown in FIG. 19(f) or FIG. 19(k), the mask pattern 301A is thenetched using the second resist pattern 303A as a mask, thereby formingan opening 304 in the mask pattern 301A.

Thereafter, the transparent substrate 300 is etched using the secondresist pattern 303A as a mask. Thus, as shown in FIG. 19(g) or FIG.19(l), the transparent substrate 300 located under the opening 304 isremoved down to such a depth that provides the light transmittedtherethrough with phase inversion of 180 degrees with respect to theexposure light. The second resist pattern 303A is then removed. At thistime, the transparent substrate 300 is etched so that the mask pattern301A slightly overhangs the etched portion of the transparent substrate300.

As has been described above, according to the third embodiment, the maskpattern 301A is first formed by patterning the light-shielding film 301on the transparent substrate 300, and then the opening 304 located inthe mask-enhancer formation region is formed in the mask pattern 301A.Thereafter, the transparent substrate 300 located under the opening 304is etched. This enables the phase difference to be provided between themask enhancer and the transparent substrate 300 located outside the maskpattern 301A, i.e., the light-transmitting region. Therefore, thephotomask of the first embodiment can be formed by setting the width ofthe opening 304, i.e., the width of the mask enhancer, such that thelight-shielding property of the mask enhancer becomes at least about thesame as that of the light-shielding film having the same width.

Important parameters in the photomask of the first embodiment are thewidth of the light-shielding pattern including the mask enhancer, i.e.,the width (L×M) of the mask pattern 301A including the opening 304, andthe width of the mask enhancer, i.e., the width (W×M) of the opening 304(see FIG. 19(g)).

According to the third embodiment, the patterning step for forming themask pattern 301A is conducted independently of the patterning step forforming the opening 304. This enables accurate dimensional control ofthe light-shielding pattern and the mask enhancer, whereby the photomaskof the first embodiment can be reliably produced.

Note that, although the third embodiment uses quartz glass as a materialof the transparent substrate 300, the present invention is not limitedto this, and calcium fluoride or the like may alternatively be used.

Although the third embodiment uses a chromium compound as a material ofthe light-shielding film 301, the present invention is not limited tothis, and a metal such as chromium, silicon or zirconium, a compoundthereof or the like may alternatively be used.

In the third embodiment, it is preferable that W·0.4×λ/NA, when thewidth of the opening 304, i.e., the width of the mask enhancer, is(W×M). In this case, it is ensured that the mask enhancer has at leastabout the same light-shielding property as that of the light-shieldingfilm having the same width.

In the third embodiment, it is preferable that L·0.8×λ/NA, when thewidth of the mask pattern 301A including the opening 304, i.e., thewidth of the light-shielding pattern, is (L×M). In this case, the effectof improving the light-shielding property is obtained by the opening304, i.e., the mask enhancer, formed in the mask pattern 301A. WhenW·(0.8×λ/NA)−L and W·L or W·L−2E (where (E×M) is the minimum possibledimension to be implemented on the photomask), the effect of improvingthe light-shielding property is reliably obtained. When0.5×(((0.8×λ/NA)−L)/2)·W·1.5×(((0.8×λ/NA)−L)/2) and W·L or W·L−2E, theeffect of improving the light-shielding property can be enhanced.Moreover, when W=((0.8×λ/NA)−L)/2 (where L·(0.8×λ/NA)/3), the effect ofimproving the light-shielding property can be maximized.

In the third embodiment, the transparent substrate 300 located under theopening 304 is removed down to such a depth that provides the lighttransmitted therethrough with phase inversion of 180 degrees withrespect to the exposure light. Alternatively, the transparent substrate300 located under the opening 304 may be removed down to such a depththat provides the light transmitted therethrough with phase inversion of(170+360×n) to (190+360×n) degrees (where n is an integer) with respectto the exposure light.

In the third embodiment, the entire transparent substrate 300 may besubjected to etching after the step of FIG. 19(g) so that thetransmittance can be adjusted with the transparent substrate 300 havingan equivalent surface condition both in the light-transmitting regionand the mask enhancer portion.

In the third embodiment, the patterning step for forming the opening 304(FIG. 19(f)) is conducted after the patterning step for forming the maskpattern 301A (FIG. 19(c)). Alternatively, the patterning step forforming the mask pattern 301A may be conducted after the patterning stepfor forming the opening 304.

Hereinafter, advantages of the photomask producing method of the thirdembodiment over the conventional photomask producing method, i.e.,advantages obtained by the characteristics of the mask enhancer, will bedescribed.

First, in the case where the transparent substrate is etched by theconventional photomask producing method so as to form a groove servingas a phase shifter, it is difficult to form the groove with a verticalwall surface. Therefore, it is impossible to provide the transmittedlight with an abrupt phase change at the boundary between thelight-transmitting region and the phase shifter. As a result, asufficient phase shift effect cannot be obtained. In contrast, in thethird embodiment, the transparent substrate 300 located under theopening 304 is etched so as to form a groove serving as a mask enhancer.The dimension of the mask enhancer can be controlled by the width of theopening 304. Therefore, as shown in FIG. 19(g), the transparentsubstrate 300 located under the opening 304 is etched such that the maskpattern 301A slightly overhangs the etched portion of the substrate 300.In other words, the groove serving as the mask enhancer is formed so asto extend under the mask pattern 301A. In this case, the resultanteffect is the same as that obtained when a groove having a completelyvertical wall surface is formed under the opening 304 as a maskenhancer. In other words, the light-shielding effect of the maskenhancer can be realized without being affected by the wall surfaceprofile of the groove formed by etching of the transparent substrate300.

Second, in producing a phase shift mask, it is generally impossible torepair the etching residues, defects or the like resulting from etchingof the substrate for forming a phase shifter. Therefore, a sufficientphase shift effect cannot be obtained. In the third embodiment as well,defects or the like may possibly be produced by etching the substratefor forming a mask enhancer. However, the mask enhancer is intended toprovide the effect of improving the light-shielding property, and it isless likely that the defects in the mask enhancer significantly affectthe effect of improving the light-shielding property. Accordingly,repairing of the defects in the mask enhancer is less likely to berequired, and thus reduction in yield is less likely to occur in theproduction of the phase shift mask.

FIG. 20(a) shows the state where a defect (white defect) causing nophase inversion is present within the mask enhancer of the photomask ofthe first embodiment. As shown in FIG. 20(a), a light-shielding filmregion 351 is formed on a transparent substrate 350 so as to surround amask enhancer 352, and the light-shielding pattern is formed from thelight-shielding film region 351 and the mask enhancer 352. A defect 353causing no phase inversion has been produced in the mask enhancer 352.The width of the light-shielding film region 351 including the maskenhancer 352 is (L×M), the width of the mask enhancer 352 is (W×M), andthe width of the defect 353 is (P×M).

FIGS. 20(b) to (d) show the simulation result of light intensity(relative light intensity) distribution of the light transmitted betweentwo points A and B of the mask of FIG. 20(a), wherein the width L was0.10 μm, 0.14 μm and 0.18 μm, respectively, and the width P was variedwith respect to the width W that maximizes the light-shielding effect ofthe mask enhancer 352 (optical conditions: wavelength λ=0.193 μm;numerical aperture NA=0.6; and coherence σ=0.8).

As shown in FIGS. 20(b) to (d), even if the defect 353 having a width Pof about 0.05 μm or less is present within the mask enhancer 352, theresultant light intensity distribution is approximately the same as thatobtained when there is no defect 353. Thus, the effect of improving thelight-shielding property is not degraded. In other words, the maskenhancer structure is immune to the defects of no phase inversion havinga width of up to about 0.05 μm.

FIG. 21(a) shows the state where an etching residue of thelight-shielding film (black defect or debris defect) is left within themask enhancer of the photomask of the first embodiment. As shown in FIG.21(a), a light-shielding film region 361 is formed on a transparentsubstrate 360 so as to surround a mask enhancer 362, and thelight-shielding pattern is formed from the light-shielding film region361 and the mask enhancer 362. An etching residue 363 of thelight-shielding film is left within the mask enhancer 362. The width ofthe light-shielding film region 361 including the mask enhancer 362 is(L×M), the width of the mask enhancer 362 is (W×M), and the width of theetching residue 363 is (P×M).

FIGS. 21(b) to (d) show the simulation result of light intensity(relative light intensity) distribution of the light transmitted betweentwo points A and B of the mask of FIG. 21(a), wherein the width L was0.10 μm, 0.14 μm and 0.18 μm, respectively, and the width P was variedwith respect to the width W that maximizes the light-shielding effect ofthe mask enhancer 362 (optical conditions: wavelength λ=0.193 μm;numerical aperture NA=0.6; and coherence σ=0.8).

As shown in FIGS. 21(b) to (d), even if the etching residue 363 having awidth P of about 0.05 μm or less is present within the mask enhancer362, the resultant light intensity distribution is approximately thesame as that obtained when there is no etching residue 363. Thus, theeffect of improving the light-shielding property is not degraded. Inother words, the mask enhancer structure is immune to the etchingresidues having a width of up to about 0.05 μm.

Third, the minimum line width of the light-shielding pattern capable ofbeing directly formed with a mask writing apparatus such as an EBlithography system is generally limited. In contrast, in the thirdembodiment, the patterning step for forming the mask pattern 301A isconducted independently of the patterning step for forming the opening304, i.e., the mask enhancer. Therefore, a fine line width up to thealignment margin of the mask writing apparatus can be used as the linewidth of the mask pattern 301A surrounding the opening 304, i.e., theline width of the light-shielding film pattern (light-shielding filmregion) surrounding the mask enhancer. For example, the alignment marginof the EB lithography system is smaller than the minimum possiblepattern width to be formed by the EB lithography system. Therefore, inthe third embodiment in which the mask pattern and the mask enhancer arerespectively formed in two separate patterning steps, a narrowerlight-shielding film pattern can be formed as compared to theconventional example. It should be noted that, since the mask patternand the mask enhancer are respectively formed in separate patterningsteps in the third embodiment, the mask enhancer may possibly bedisplaced, i.e., may not be located in the center of the mask pattern.However, as described in the first embodiment in connection with FIG.11, exposure with the photomask having a displaced mask enhancer hardlyaffects the light intensity distribution.

FIRST MODIFICATION OF THIRD EMBODIMENT

Hereinafter, a method for producing a photomask according to the firstmodification of the third embodiment of the invention will be describedwith reference to the figures.

Note that the first modification of the third embodiment is differentfrom the third embodiment in the following point: in the thirdembodiment, the patterning step for forming the opening is conductedafter the patterning step for forming the mask pattern. However, in thefirst modification of the third embodiment, the patterning step forforming the opening is conducted prior to the patterning step forforming the mask pattern.

FIGS. 22(a) to (g) are cross-sectional views illustrating the steps ofthe photomask producing method of the first modification of the thirdembodiment, respectively. FIGS. 22(h) to (k) are plan viewscorresponding to FIGS. 22(b), (c), (f) and (g), respectively.

First, as shown in FIG. 22(a), a light-shielding film 311 of, e.g., achromium compound is deposited on a transparent substrate 310 of, e.g.,quartz glass. Then, a resist is applied to the light-shielding film 311to form a first resist film 312.

Then, a pattern is written on the first resist film 312 by using a maskwriting apparatus. The first resist film 312 is then developed, wherebya first resist pattern 312A having an opening in the mask-enhancerformation region is produced as shown in FIG. 22(b) or FIG. 22(h).

Thereafter, the light-shielding film 311 is etched using the firstresist pattern 312A as a mask. As a result, as shown in FIG. 22(c) orFIG. 22(i), an opening 313 is formed in the light-shielding film 311,and then the first resist pattern 312A is removed.

As shown in FIG. 22(d), the transparent substrate 310 is then etchedusing the light-shielding film 311 with the opening 313 as a mask. Thus,the transparent substrate 310 located under the opening 313 is removeddown to such a depth that provides the light transmitted therethroughwith phase inversion of 180 degrees with respect to the exposure light.At this time, the transparent substrate 310 is etched so that thelight-shielding film 311 slightly overhangs the etched portion of thetransparent substrate 310.

Then, as shown in FIG. 22(e), a resist is applied to the light-shieldingfilm 311 including the opening 313 so as to form a second resist film314.

Thereafter, a pattern is written on the second resist film 314 by usingthe mask writing apparatus. The second resist film 314 is thendeveloped, whereby a second resist pattern 314A covering themask-pattern formation region is produced as shown in FIG. 22(f) or FIG.22(j).

The light-shielding film 311 is then etched using the second resistpattern 314A as a mask. Thus, as shown in FIG. 22(g) or FIG. 22(k), amask pattern 311A formed from the light-shielding film 311 and havingthe opening 313 is formed, and then the second resist pattern 314A isremoved.

As has been described above, according to the first modification of thethird embodiment, the opening 313 located in the mask-enhancer formationregion is first formed in the light-shielding film 311 on thetransparent substrate 310, and then the transparent substrate 310located under the opening 313 is etched. Thereafter, the mask pattern311A having the opening 313 is formed by patterning the light-shieldingfilm 311. This enables the phase difference to be provided between themask enhancer and the transparent substrate 310 located outside the maskpattern 311A, i.e., the light-transmitting region. Therefore, thephotomask of the first embodiment can be formed by setting the width ofthe opening 313, i.e., the width of the mask enhancer, such that thelight-shielding property of the mask enhancer becomes at least about thesame as that of the light-shielding film having the same width.

Moreover, according to the first modification of the third embodiment,the patterning step for forming the mask pattern 311A is conductedindependently of the patterning step for forming the opening 313. Thisenables accurate dimensional control of the mask pattern 311A includingthe opening 313, i.e., the light-shielding pattern, as well as the maskenhancer, whereby the photomask of the first embodiment can be reliablyproduced.

Moreover, according to the first modification of the third embodiment,the patterning step for forming the opening 313 is conducted prior tothe patterning step for forming the mask pattern 311A. Therefore, thetransparent substrate 310 can be etched using the light-shielding film311 with the opening 313 as a mask. This eliminates the need to conductformation of the opening and etching of the substrate successively byusing a resist pattern as in the case where the opening is formed afterformation of the mask pattern (e.g., the third embodiment). Accordingly,production of the photomask of the first embodiment is facilitated.

Moreover, according to the first modification of the third embodiment,the substrate is etched before the mask pattern 311A is formed.Therefore, no problem will occur even if the light-shielding film regionsurrounding the opening 313 is eliminated upon forming the mask pattern311A due to misalignment of the mask writing apparatus. The reason forthis is as follows: in the case of the dimension with which thelight-shielding film region may be eliminated by misalignment, theeffect of improving the light-shielding property is obtained even if thelight-shielding pattern is formed only from the phase shifter.

Advantages of the photomask producing method of the first modificationof the third embodiment over the conventional photomask producingmethod, i.e., advantages obtained by the characteristics of the maskenhancer, are the same as those of the third embodiment.

Note that, although the first modification of the third embodiment usesquartz glass as a material of the transparent substrate 310, the presentinvention is not limited to this, and calcium fluoride or the like mayalternatively be used.

Although the first modification of the third embodiment uses a chromiumcompound as a material of the light-shielding film 311, the presentinvention is not limited to this, and a metal such as chromium, siliconor zirconium, a compound thereof or the like may alternatively be used.

In the first modification of the third embodiment, it is preferable thatW·0.4×λ/NA, when the width of the opening 313, i.e., the width of themask enhancer, is (W×M).

In the first modification of the third embodiment, it is preferable thatL·0.8×λ/NA, when the width of the mask pattern 311A including theopening 313, i.e., the width of the light-shielding pattern, is (L×M).In this case, it is preferable that: W·(0.8×λ/NA)−L and W·L or W·L−2E;or 0.5×(((0.8×λ/NA)−L)/2)·W·1.5×(((0.8×λ/NA)−L)/2) and W·L or W·L−2E.

In the first modification of the third embodiment, the transparentsubstrate 310 located under the opening 313 is removed down to such adepth that provides the light transmitted therethrough with phaseinversion of 180 degrees with respect to the exposure light.Alternatively, the transparent substrate 310 located under the opening313 may be removed down to such a depth that provides the lighttransmitted therethrough with phase inversion of (170+360×n) to(190+360×n) degrees (where n is an integer) with respect to the exposurelight.

In the first modification of the third embodiment, the entiretransparent substrate 310 may be subjected to etching after the step ofFIG. 22(g) so that the transmittance can be adjusted with thetransparent substrate 310 having an equivalent surface condition both inthe light-transmitting region and the mask enhancer portion.

SECOND MODIFICATION OF THIRD EMBODIMENT

Hereinafter, a method for producing a photomask according to the secondmodification of the third embodiment of the invention will be describedwith reference to the figures.

Note that the second modification of the third embodiment is differentfrom the third embodiment in the following point: in the thirdembodiment, the transparent substrate located under the opening isremoved. However, in the second modification of the third embodiment,the transparent substrate located outside the mask pattern is removed.

FIGS. 23(a) to (h) are cross-sectional views illustrating the steps ofthe photomask producing method of the second modification of the thirdembodiment, respectively. FIGS. 23(i) to (m) are plan viewscorresponding to FIGS. 23(b), (c), (f), (g) and (h), respectively.

First, as shown in FIG. 23(a), a light-shielding film 321 of, e.g., achromium compound is deposited on a transparent substrate 320 of, e.g.,quartz glass. Then, a resist is applied to the light-shielding film 321to form a first resist film 322.

Then, a pattern is written on the first resist film 322 by using a maskwriting apparatus. The first resist film 322 is then developed, wherebya first resist pattern 322A covering the mask-pattern formation regionis produced as shown in FIG. 23(b) or FIG. 23(i).

Thereafter, the light-shielding film 321 is etched using the firstresist pattern 322A as a mask. As a result, as shown in FIG. 23(c) orFIG. 23(j), a mask pattern 321A of the light-shielding film 321 isformed, and then the first resist pattern 322A is removed.

As shown in FIG. 23(d), the transparent substrate 320 is then etchedusing the mask pattern 321A. Thus, the transparent substrate 320 locatedoutside the mask pattern 321A is removed down to such a depth thatprovides the light transmitted therethrough with phase inversion of 180degrees with respect to the exposure light. At this time, thetransparent substrate 320 is etched so that the mask pattern 321Aslightly overhangs the etched portion of the transparent substrate 320.

Then, as shown in FIG. 23(e), a resist is applied to the transparentsubstrate 320 including the mask pattern 321A so as to form a secondresist film 323.

Thereafter, a pattern is written on the second resist film 323 by usingthe mask writing apparatus. The second resist film 323 is thendeveloped, whereby a second resist pattern 323A having an opening in themask-enhancer formation region is produced as shown in FIG. 23(f) orFIG. 23(k).

As shown in FIG. 23(g) or FIG. 23(l), the mask pattern 321A is thenetched using the second resist pattern 323A as a mask. Thus, an opening324 is formed in the mask pattern 321A, and then the second resistpattern 323A is removed as shown in FIG. 23(h) or FIG. 23(m).

As has been described above, according to the second modification of thethird embodiment, the mask pattern 321A is formed by patterning thelight-shielding film 321 on the transparent substrate 320, and then thetransparent substrate 320 located outside the mask pattern 321A isetched. Thereafter, the opening 324 located in the mask-enhancerformation region is formed in the mask pattern 321A. This enables thephase difference to be provided between the mask enhancer and thetransparent substrate 320 located outside the mask pattern 321A, i.e.,the light-transmitting region. Therefore, the photomask of the firstembodiment can be formed by setting the width of the opening 324, i.e.,the width of the mask enhancer, such that the light-shielding propertyof the mask enhancer becomes at least about the same as that of thelight-shielding film having the same width.

Moreover, according to the second modification of the third embodiment,the patterning step for forming the mask pattern 321A is conductedindependently of the patterning step for forming the opening 324. Thisenables accurate dimensional control of the mask pattern 321A includingthe opening 324, i.e., the light-shielding pattern, as well as the maskenhancer, whereby the photomask of the first embodiment can be reliablyproduced.

Moreover, according to the second modification of the third embodiment,the phase difference is provided between the mask enhancer and thelight-transmitting region by etching the transparent substrate 320located outside the mask pattern 321A. Therefore, production of thephotomask of the first embodiment is facilitated as compared to the casewhere the phase difference is provided by etching the transparentsubstrate located under the opening having a small area (the thirdembodiment or the first modification thereof).

Moreover, according to the second modification of the third embodiment,the substrate is etched before the opening 324 is formed. Therefore, noproblem will occur even if the light-shielding film region surroundingthe opening 324 is eliminated upon forming the opening 324 due tomisalignment of the mask writing apparatus. The reason for this is asfollows: in the case of the dimension with which the light-shieldingfilm region may be eliminated by misalignment, the effect of improvingthe light-shielding property is obtained even if the light-shieldingpattern is formed only from the phase shifter.

Advantages of the photomask producing method of the second modificationof the third embodiment over the conventional photomask producingmethod, i.e., advantages obtained by the characteristics of the maskenhancer, are the same as those of the third embodiment.

Note that, although the second modification of the third embodiment usesquartz glass as a material of the transparent substrate 320, the presentinvention is not limited to this, and calcium fluoride or the like mayalternatively be used.

Although the second modification of the third embodiment uses a chromiumcompound as a material of the light-shielding film 321, the presentinvention is not limited to this, and a metal such as chromium, siliconor zirconium, a compound thereof or the like may alternatively be used.

In the second modification of the third embodiment, it is preferablethat W·0.4×λ/NA, when the width of the opening 324, i.e., the width ofthe mask enhancer, is (W×M).

In the second modification of the third embodiment, it is preferablethat L·0.8×λ/NA, when the width of the mask pattern 321A including theopening 324, i.e., the width of the light-shielding pattern, is (L×M).In this case, it is preferable that: W·(0.8×λ/NA)−L and W·L or W·L−2E;or 0.5×(((0.8×λ/NA)−L)/2)·W·1.5×(((0.8×λ/NA)−L)/2) and W·L or W·L−2E.

In the second modification of the third embodiment, the transparentsubstrate 320 located outside the mask pattern 321A is removed down tosuch a depth that provides the light transmitted therethrough with phaseinversion of 180 degrees with respect to the exposure light.Alternatively, the transparent substrate 320 located outside the maskpattern 321A may be removed down to such a depth that provides the lighttransmitted therethrough with phase inversion of (170+360×n) to(190+360×n) degrees (where n is an integer) with respect to the exposurelight.

In the second modification of the third embodiment, the entiretransparent substrate 320 may be subjected to etching after the step ofFIG. 23(h) so that the transmittance can be adjusted with thetransparent substrate 320 having an equivalent surface condition both inthe light-transmitting region and the mask enhancer portion.

FOURTH EMBODIMENT

Hereinafter, a method for producing a photomask according to the fourthembodiment of the invention will be described with reference to thefigures. Note that the photomask producing method of the fourthembodiment is a method for producing the photomask of the firstembodiment, i.e., a photomask including an isolated light-shieldingpattern formed from a light-shielding film region and a mask enhancer ona transparent substrate. In the fourth embodiment, NA is a numericalaperture of a reduction projection optical system of an aligner, λ is awavelength of exposure light, i.e., a light source, and M is amagnification of the reduction projection optical system of the aligner.

FIGS. 24(a) to (g) are cross-sectional views illustrating the steps ofthe photomask producing method of the fourth embodiment, respectively.FIGS. 24(h) to (l) are plan views corresponding to FIGS. 24(b), (c),(e), (f) and (g), respectively.

First, as shown in FIG. 24(a), a phase shifter layer 401 of, e.g., anSOG (Spin on Glass) film is formed on a transparent substrate 400 of,e.g., quartz glass so as to have such a thickness that provides thelight transmitted:

therethrough with phase inversion of 180 degrees with respect to theexposure light. Then, a light-shielding film 402 of, e.g., a chromiumcompound is deposited on the phase shifter layer 401, and a resist isapplied to the light-shielding film 402 to form a first resist film 403.

Then, a pattern is written on the first resist film 403 by using a maskwriting apparatus. The first resist film 403 is then developed, wherebya first resist pattern 403A covering the mask-pattern formation regionis produced as shown in FIG. 24(b) or FIG. 24(h).

Thereafter, the light-shielding film 402 is etched using the firstresist pattern 403A as a mask. As a result, as shown in FIG. 24(c) orFIG. 24(i), a mask pattern 402A of the light-shielding film 402 isformed, and then the first resist pattern 403A is removed.

As shown in FIG. 24(d), a resist is applied to the transparent substrate400 having the mask pattern 402A thereon, thereby forming a secondresist film 404.

Thereafter, a pattern is written on the second resist film 404 by usingthe mask writing apparatus. The second resist film 404 is thendeveloped, whereby a second resist pattern 404A having an opening in themask-enhancer formation region is produced as shown in FIG. 24(e) orFIG. 24(j).

As shown in FIG. 24(f) or FIG. 24(k), the mask pattern 402A and thephase shifter layer 401 are sequentially etched using the second resistpattern 404A as a mask, whereby an opening 405 is formed in the maskpattern 402A, as well as the phase shifter layer 401 located under theopening 405 is removed. The second resist pattern 404A is then removedas shown in FIG. 24(g) or FIG. 24(l).

As has been described above, according to the fourth embodiment, themask pattern 402A is formed by patterning the light-shielding film 402on the phase shifter layer 401 formed on the transparent substrate 400.Thereafter, the opening 405 located in the mask-enhancer formationregion is formed in the mask pattern 402A, and the phase shifter layer401 located under the opening 405 is then removed. This enables thephase difference to be provided between the mask enhancer and thetransparent substrate 400 located outside the mask pattern 402A, i.e.,the light-transmitting region. Therefore, the photomask of the firstembodiment can be formed by setting the width of the opening 405, i.e.,the width of the mask enhancer, such that the light-shielding propertyof the mask enhancer becomes at least about the same as that of thelight-shielding film having the same width.

Moreover, according to the fourth embodiment, the patterning step forforming the mask pattern 402A is conducted independently of thepatterning step for forming the opening 405. This enables accuratedimensional control of the mask pattern 402A including the opening 405,i.e., the light-shielding pattern, as well as the mask enhancer, wherebythe photomask of the first embodiment can be reliably produced.

Moreover, according to the fourth embodiment, the phase difference isprovided between the light-transmitting region and the mask enhancer byremoving the phase shifter layer 401 located under the opening 405. Thisfacilitates management of the etching step as compared to the case wherethe phase difference is provided by etching the transparent substrate400. Thus, the phase error is reduced as well as the phase shifter layer401 with a vertical edge can be easily formed.

Moreover, according to the fourth embodiment, the light-shieldingpattern is not necessarily be required for etching the phase shifterlayer 401, as opposed to the case of etching the transparent substrate400. Therefore, no problem will occur even if the light-shielding filmregion surrounding the opening 405 is eliminated upon forming theopening 405 due to misalignment of the mask writing apparatus.

Advantages of the photomask producing method of the fourth embodimentover the conventional photomask producing method, i.e., advantagesobtained by the characteristics of the mask enhancer, are the same asthose of the third embodiment.

Note that, although the fourth embodiment uses quartz glass as amaterial of the transparent substrate 400, the present invention is notlimited to this, and calcium fluoride or the like may alternatively beused.

Although the fourth embodiment uses as a material of the phase shifterlayer 401 an SOG film that provides the light transmitted therethroughwith phase inversion of 180 degrees with respect to the exposure light,the present invention is not limited to this, and any transparent filmthat provides the light transmitted therethrough with phase inversion of(170+360×n) to (190+360×n) degrees (where n is an integer) with respectto the exposure light may be used.

Although the fourth embodiment uses a chromium compound as a material ofthe light-shielding film 402, the present invention is not limited tothis, and a metal such as chromium, silicon or zirconium, a compoundthereof or the like may alternatively be used.

In the fourth embodiment, it is preferable that W·0.4×λ/NA, when thewidth of the opening 405, i.e., the width of the mask enhancer, is(W×M).

In the fourth embodiment, it is preferable that L·0.8×λ/NA, when thewidth of the mask pattern 402A including the opening 405, i.e., thewidth of the light-shielding pattern, is (L×M). In this case, it ispreferable that: W·(0.8×λ/NA)−L and W·L or W·L−2E; or0.5×(((0.8×λ/NA)−L)/2)·W·1.5×(((0.8×λ/NA)−L)/2) and W·L or W·L−2E.

FIRST MODIFICATION OF FOURTH EMBODIMENT

Hereinafter, a method for producing a photomask according to the firstmodification of the fourth embodiment of the invention will be describedwith reference to the figures.

Note that the first modification of the fourth embodiment is differentfrom the fourth embodiment in the following point: in the fourthembodiment, the phase shifter layer located under the opening isremoved. However, in the first modification of the fourth embodiment,the phase shifter layer located outside the mask pattern is removed.

FIGS. 25(a) to (h) are cross-sectional views illustrating the steps ofthe photomask producing method of the first modification of the fourthembodiment, respectively. FIGS. 25(i) to (n) are plan viewscorresponding to FIGS. 25(b), (c), (d), (f), (g) and (h), respectively.

First, as shown in FIG. 25(a), a phase shifter layer 411 of, e.g., anSOG (Spin on Glass) film is formed on a transparent substrate 410 of,e.g., quartz glass so as to have such a thickness that provides thelight transmitted therethrough with phase inversion of 180 degrees withrespect to the exposure light. Then, a light-shielding film 412 of,e.g., a chromium compound is deposited on the phase shifter layer 411,and a resist is applied to the light-shielding film 412 to form a firstresist film 413.

Then, a pattern is written on the first resist film 413 by using a maskwriting apparatus. The first resist film 413 is then developed, wherebya first resist pattern 413A covering the mask-pattern formation regionis produced as shown in FIG. 25(b) or FIG. 25(i).

Thereafter, the light-shielding film 412 is etched using the firstresist pattern 413A as a mask. As a result, as shown in FIG. 25(c) orFIG. 25(j), a mask pattern 412A of the light-shielding film 412 isformed, and then the first resist pattern 413A is removed.

As shown in FIG. 25(d) or FIG. 25(k), the phase shifter layer 411 isthen etched using the mask pattern 412A, so that the phase shifter layer411 located outside the mask pattern 412A is removed.

As shown in FIG. 25(e), a resist is then applied to the transparentsubstrate 410 including the mask pattern 412A, thereby forming a secondresist film 414.

Thereafter, a pattern is written on the second resist film 414 by usingthe mask writing apparatus. The second resist film 414 is thendeveloped, whereby a second resist pattern 414A having an opening in themask-enhancer formation region is formed as shown in FIG. 25(f) or FIG.25(l).

As shown in FIG. 25(g) or FIG. 25(m), the mask pattern 412A is etchedusing the second resist pattern 414A as a mask, whereby an opening 415is formed in the mask pattern 412A. The second resist pattern 414A isthen removed as shown in FIG. 25(h) or FIG. 25(n).

As has been described above, according to the first modification of thefourth embodiment, the mask pattern 412A is formed by patterning thelight-shielding film 412 on the phase shifter layer 411 formed on thetransparent substrate 410. Thereafter, the phase shifter layer 411located outside the mask pattern 412A is removed, and the opening 415located in the mask enhancer formation region is then formed in the maskpattern 412A. This enables the phase difference to be provided betweenthe mask enhancer and the transparent substrate 410 located outside themask pattern 412A, i.e., the light-transmitting region. Therefore, thephotomask of the first embodiment can be formed by setting the width ofthe opening 415, i.e., the width of the mask enhancer, such that thelight-shielding property of the mask enhancer becomes at least about thesame as that of the light-shielding film having the same width.

Moreover, according to the first modification of the fourth embodiment,the patterning step for forming the mask pattern 412A is conductedindependently of the patterning step for forming the opening 415. Thisenables accurate dimensional control of the mask pattern 412A includingthe opening 415, i.e., the light-shielding pattern, as well as the maskenhancer, whereby the photomask of the first embodiment can be reliablyproduced.

Moreover, according to the first modification of the fourth embodiment,the phase difference is provided between the light-transmitting regionand the mask enhancer by removing the phase shifter layer 411 locatedoutside the mask pattern 412A. This facilitates management of theetching step as compared to the case where the phase difference isprovided by etching the transparent substrate 410. Thus, the phase erroris reduced as well as the phase shifter layer 411 with a vertical edgecan be easily formed. Moreover, production of the photomask of the firstembodiment is facilitated as compared to the case where the phasedifference is provided by removing the phase shifter layer 411 locatedunder the opening 415 having a small area. Moreover, the phase shifterlayer 411 is etched using the mask pattern 412A in which the opening 415has not yet been formed. This eliminates the need to conduct formationof the mask pattern and etching of the shifter layer successively byusing a resist pattern as in the case where the mask pattern is formedafter formation of the opening. Accordingly, production of the photomaskof the first embodiment is facilitated.

Advantages of the photomask producing method of the first modificationof the fourth embodiment over the conventional photomask producingmethod, i.e., advantages obtained by the characteristics of the maskenhancer, are the same as those of the third embodiment.

Note that, although the first modification of the fourth embodiment usesquartz glass as a material of the transparent substrate 410, the presentinvention is not limited to this, and calcium fluoride or the like mayalternatively be used.

Although the first modification of the fourth embodiment uses as amaterial of the phase shifter layer 411 an SOG film that provides thelight transmitted therethrough with phase inversion of 180 degrees withrespect to the exposure light, the present invention is not limited tothis, and any transparent film that provides the light transmittedtherethrough with phase inversion of (170+360×n) to (190+360×n) degrees(where n is an integer) with respect to the exposure light may be used.

Although the first modification of the fourth embodiment uses a chromiumcompound as a material of the light-shielding film 412, the presentinvention is not limited to this, and a metal such as chromium, siliconor zirconium, a compound thereof or the like may alternatively be used.

In the first modification of the fourth embodiment, it is preferablethat W·0.4×λ/NA, when the width of the opening 415, i.e., the width ofthe mask enhancer, is (W×M).

In the first modification of the fourth embodiment, it is preferablethat L·0.8×λ/NA, when the width of the mask pattern 412A including theopening 415, i.e., the width of the light-shielding pattern, is (L×M).In this case, it is preferable that: W·(0.8×λ/NA)−L and W·L or W·L−2E;or 0.5×(((0.8×λ/NA)−L)/2)·W·1.5×(((0.8×λ/NA)−L)/2) and W·L or W·L−2E.

SECOND MODIFICATION OF FOURTH EMBODIMENT

Hereinafter, a method for producing a photomask according to the secondmodification of the fourth embodiment of the invention will be describedwith reference to the figures.

Note that the second modification of the fourth embodiment is differentfrom the fourth embodiment in the following point: in the fourthembodiment, the patterning step for forming the opening is conductedafter the patterning step for forming the mask pattern, and the phaseshifter layer located under the opening is removed. However, in thesecond modification of the fourth embodiment, the patterning step forforming the opening is conducted before the patterning step for formingthe mask pattern, and the phase shifter layer located outside the maskpattern is removed.

FIGS. 26(a) to (g) are cross-sectional views illustrating the steps ofthe photomask producing method of the second modification of the fourthembodiment, respectively. FIGS. 26(h) to (k) are plan viewscorresponding to FIGS. 26(b), (c), (e) and (g), respectively.

First, as shown in FIG. 26(a), a phase shifter layer 421 of, e.g., anSOG film is formed on a transparent substrate 420 of, e.g., quartz glassso as to have such a thickness that provides the light transmittedtherethrough with phase inversion of 180 degrees with respect to theexposure light. Then, a light-shielding film 422 of, e.g., a chromiumcompound is deposited on the phase shifter layer 421, and a resist isapplied to the light-shielding film 422 to form a first resist film 423.

Then, a pattern is written on the first resist film 423 by using a maskwriting apparatus. The first resist film 423 is then developed, wherebya first resist pattern 423A having an opening in the mask-enhancerformation region is formed as shown in FIG. 26(b) or FIG. 26(h).

Thereafter, the light-shielding film 422 is etched using the firstresist pattern 423A as a mask. As a result, as shown in FIG. 26(c) orFIG. 26(i), an opening 424 is formed in the light-shielding film 422,and then the first resist pattern 423A is removed.

As shown in FIG. 26(d), a resist is then applied to the light-shieldingfilm 422 including the opening 424, thereby forming a second resist film425.

Thereafter, a pattern is written on the second resist film 425 by usingthe mask writing apparatus. The second resist film 425 is thendeveloped, whereby a second resist pattern 425A covering themask-pattern formation region is produced as shown in FIG. 26(e) or FIG.26(j).

As shown in FIG. 26(f), the light-shielding film 422 and the phaseshifter layer 421 are sequentially etched using the second resistpattern 425A as a mask. As a result, a mask pattern 422A formed from thelight-shielding film 422 and having the opening 424 is formed, as wellas the phase shifter layer 421 located outside the mask pattern 422A isremoved. As shown in FIG. 26(g) or FIG. 26(k), the second resist pattern425A is then removed.

As has been described above, according to the second modification of thefourth embodiment, the opening 424 located in the mask-enhancerformation region is formed in the light-shielding film 422 on the phaseshifter layer 421 formed on the transparent substrate 420. Thereafter,the mask pattern 422A having the opening 424 is formed by patterning thelight-shielding film 422, and the phase shifter layer 421 locatedoutside the mask pattern 422A is then removed. This enables the phasedifference to be provided between the mask enhancer and the transparentsubstrate 420 located outside the mask pattern 422A, i.e., thelight-transmitting region. Therefore, the photomask of the firstembodiment can be formed by setting the width of the opening 424, i.e.,the width of the mask enhancer, such that the light-shielding propertyof the mask enhancer becomes at least about the same as that of thelight-shielding film having the same width.

Moreover, according to the second modification of the fourth embodiment,the patterning step for forming the mask pattern 422A is conductedindependently of the patterning step for forming the opening 424. Thisenables accurate dimensional control of the mask pattern 422A includingthe opening 424, i.e., the light-shielding pattern, as well as the maskenhancer, whereby the photomask of the first embodiment can be reliablyproduced.

Moreover, according to the second modification of the fourth embodiment,the phase difference is provided between the light-transmitting regionand the mask enhancer by removing the phase shifter layer 421 locatedoutside the mask pattern 422A. This facilitates management of theetching step as compared to the case where the phase difference isprovided by etching the transparent substrate 420. Thus, the phase erroris reduced as well as the phase shifter layer 421 with a vertical edgecan be easily formed. Moreover, production of the photomask of the firstembodiment is facilitated as compared to the case where the phasedifference is provided by removing the phase shifter layer 421 locatedunder the opening 424 having a small area.

Moreover, according to the second modification of the fourth embodiment,the light-shielding pattern is not necessarily be required for etchingthe phase shifter layer 421, as opposed to the case of etching thetransparent substrate 420. Therefore, no problem will occur even if thelight-shielding film region surrounding the opening 424 is eliminatedupon forming the mask pattern 422A due to misalignment of the maskwriting apparatus.

Advantages of the photomask producing method of the second modificationof the fourth embodiment over the conventional photomask producingmethod, i.e., advantages obtained by the characteristics of the maskenhancer, are the same as those of the third embodiment.

Note that, although the second modification of the fourth embodimentuses quartz glass as a material of the transparent substrate 420, thepresent invention is not limited to this, and calcium fluoride or thelike may alternatively be used.

Although the second modification of the fourth embodiment uses as amaterial of the phase shifter layer 421 an SOG film that provides thelight transmitted therethrough with phase inversion of 180 degrees withrespect to the exposure light, the present invention is not limited tothis, and any transparent film that provides the light transmittedtherethrough with phase inversion of (170+360×n) to (190+360×n) degrees(where n is an integer) with respect to the exposure light may be used.

Although the second modification of the fourth embodiment uses achromium compound as a material of the light-shielding film 422, thepresent invention is not limited to this, and a metal such as chromium,silicon or zirconium, a compound thereof or the like may alternativelybe used.

In the second modification of the fourth embodiment, it is preferablethat W·0.4×λ/NA, when the width of the opening 424, i.e., the width ofthe mask enhancer, is (w×M).

In the second modification of the fourth embodiment, it is preferablethat L·0.8×λ/NA, when the width of the mask pattern 422A including theopening 424, i.e., the width of the light-shielding pattern, is (L×M).In this case, it is preferable that: W·(0.8×λ/NA)−L and W·L or W·L−2E;or 0.5×(((0.8×λ/NA)−L)/2)·W·1.5×(((0.8×λ/NA)−L)/2) and W·L or W·L−2E.

THIRD MODIFICATION OF FOURTH EMBODIMENT

Hereinafter, a method for producing a photomask according to the thirdmodification of the fourth embodiment of the invention will be describedwith reference to the figures.

Note that the third modification of the fourth embodiment is differentfrom the fourth embodiment in the following point: in the fourthembodiment, the patterning step for forming the opening is conductedafter the patterning step for forming the mask pattern. However, in thethird modification of the fourth embodiment, the patterning step forforming the opening is conducted before the patterning step for formingthe mask pattern.

FIGS. 27(a) to (g) are cross-sectional views illustrating the steps ofthe photomask producing method of the third modification of the fourthembodiment, respectively. FIGS. 27(h) to (l) are plan viewscorresponding to FIGS. 27(b), (c), (d), (f) and (g), respectively.

First, as shown in FIG. 27(a), a phase shifter layer 431 of, e.g., anSOG film is formed on a transparent substrate 430 of, e.g., quartz glassso as to have such a thickness that provides the light transmittedtherethrough with phase inversion of 180 degrees with respect to theexposure light. Then, a light-shielding film 432 of, e.g., a chromiumcompound is deposited on the phase shifter layer 431, and a resist isapplied to the light-shielding film 432 to form a first resist film 433.

Then, a pattern is written on the first resist film 433 by using a maskwriting apparatus. The first resist film 433 is then developed, wherebya first resist pattern 433A having an opening in the mask-enhancerformation region is formed as shown in FIG. 27(b) or FIG. 27(h).

Thereafter, the light-shielding film 432 is etched using the firstresist pattern 433A as a mask. As a result, as shown in FIG. 27(c) orFIG. 27(i), an opening 434 is formed in the light-shielding film 432,and then the first resist pattern 433A is removed.

As shown in FIG. 27(d) or FIG. 27(j), the phase shifter layer 431 isthen etched using the light-shielding film 432 having the opening 434 asa mask, so that the phase shifter layer 431 located outside the opening434 is removed.

As shown in FIG. 27(e), a resist is then applied to the light-shieldingfilm 432 including the opening 434, thereby forming a second resist film435.

Thereafter, a pattern is written on the second resist film 435 by usingthe mask writing apparatus. The second resist film 435 is thendeveloped, whereby a second resist pattern 435A covering themask-pattern formation region is produced as shown in FIG. 27(f) or FIG.27(k).

The light-shielding film 432 is then etched using the second resistpattern 435A as a mask. As a result, as shown in FIG. 27(g) or FIG.27(l), the mask pattern 432A formed from the light-shielding film 432and having the opening 434 is formed, and then the second resist pattern435A is removed.

As has been described above, according to the third modification of thefourth embodiment, the opening 434 located in the mask-enhancerformation region is formed in the light-shielding film 432 on the phaseshifter layer 431 formed on the transparent substrate 430. Thereafter,the phase shifter layer 431 located under the opening 434 is removed,and the mask pattern 432A having the opening 434 is then formed bypatterning the light-shielding film 432. This enables the phasedifference to be provided between the mask enhancer and the transparentsubstrate 430 located outside the mask pattern 432A, i.e., thelight-transmitting region. Therefore, the photomask of the firstembodiment can be formed by setting the width of the opening 434, i.e.,the width of the mask enhancer, such that the light-shielding propertyof the mask enhancer becomes at least about the same as that of thelight-shielding film having the same width.

Moreover, according to the third modification of the fourth embodiment,the patterning step for forming the mask pattern 432A is conductedindependently of the patterning step for forming the opening 434. Thisenables accurate dimensional control of the mask pattern 432A includingthe opening 434, i.e., the light-shielding pattern, as well as the maskenhancer, whereby the photomask of the first embodiment can be reliablyproduced.

Moreover, according to the third modification of the fourth embodiment,the phase difference is provided between the light-transmitting regionand the mask enhancer by removing the phase shifter layer 431 locatedoutside the opening 434. This facilitates management of the etching stepas compared to the case where the phase difference is provided byetching the transparent substrate 430. Thus, the phase error is reducedas well as the phase shifter layer 431 with a vertical edge can beeasily formed.

Moreover, according to the third modification of the fourth embodiment,the patterning step for forming the opening 434 is conducted before thepatterning step for forming the mask pattern 432A. Therefore, the phaseshifter layer 431 can be etched using the light-shielding film 432having the opening 434 as a mask. This eliminates the need to conductformation of the opening and etching of the substrate successively byusing a resist pattern as in the case where the opening is formed afterformation of the mask pattern (e.g., the fourth embodiment).Accordingly, production of the photomask of the first embodiment isfacilitated.

Advantages of the photomask producing method of the third modificationof the fourth embodiment over the conventional photomask producingmethod, i.e., advantages obtained by the characteristics of the maskenhancer, are the same as those of the third embodiment.

Note that, although the third modification of the fourth embodiment usesquartz glass as a material of the transparent substrate 430, the presentinvention is not limited to this, and calcium fluoride or the like mayalternatively be used.

Although the third modification of the fourth embodiment uses as amaterial of the phase shifter layer 431 an SOG film that provides thelight transmitted therethrough with phase inversion of 180 degrees withrespect to the exposure light, the present invention is not limited tothis, and any transparent film that provides the light transmittedtherethrough with phase inversion of (170+360×n) to (190+360×n) degrees(where n is an integer) with respect to the exposure light may be used.

Although the third modification of the fourth embodiment uses a chromiumcompound as a material of the light-shielding film 432, the presentinvention is not limited to this, and a metal such as chromium, siliconor zirconium, a compound thereof or the like may alternatively be used.

In the third modification of the fourth embodiment, it is preferablethat W·0.4×λ/NA, when the width of the opening 434, i.e., the width ofthe mask enhancer, is (W×M).

In the third modification of the fourth embodiment, it is preferablethat L·0.8×λ/NA, when the width of the mask pattern 422A including theopening 434, i.e., the width of the light-shielding pattern, is (L×M).In this case, it is preferable that: W·(0.8×λ/NA)−L and W·L or W·L−2E;or 0.5×(((0.8×λ/NA)−L)/2)·W·1.5×(((0.8×λ/NA)−L)/2) and W·L or W·L−2E.

FIFTH EMBODIMENT

Hereinafter, a method for producing a photomask according to the fifthembodiment of the invention will be described with reference to thefigures. Note that the photomask producing method of the fifthembodiment is a method for producing the photomask of the firstembodiment, i.e., a photomask including an isolated light-shieldingpattern formed from a light-shielding film region and a mask enhancer ona transparent substrate. In the fifth embodiment, NA is a numericalaperture of a reduction projection optical system of an aligner, λ is awavelength of exposure light, i.e., a light source, and M is amagnification of the reduction projection optical system of the aligner.

FIGS. 28(a) to (g) are cross-sectional views illustrating the steps ofthe photomask producing method of the fifth embodiment, respectively.FIGS. 28(h) to (l) are plan views corresponding to FIGS. 28(b), (c),(e), (f) and (g), respectively.

First, as shown in FIG. 28(a), a light-shielding film 501 of, e.g., achromium compound is deposited on a transparent substrate 500 of, e.g.,quartz glass. Then, a resist is applied to the light-shielding film 501to form a first resist film 502.

Then, a pattern is written on the first resist film 502 by using a maskwriting apparatus. The first resist film 502 is then developed, wherebya first resist pattern 502A having an opening in the mask-enhancerformation region is formed as shown in FIG. 28(b) or FIG. 28(h).

Thereafter, the light-shielding film 501 is etched using the firstresist pattern 502A as a mask. As a result, as shown in FIG. 28(c) orFIG. 28(i), an opening 503 is formed in the light-shielding film 501,and then the first resist pattern 502A is removed.

As shown in FIG. 28(d), a phase shifter layer 504 of, e.g., an SOG filmis formed on the light-shielding film 501 including the opening 503 soas to have such a thickness that provides the light transmittedtherethrough with phase inversion of 180 degrees with respect to theexposure light. Then, a resist is applied to the phase shifter layer 504to form a second resist film 505.

Then, a pattern is written on the second resist film 505 by using a maskwriting apparatus. The second resist film 505 is then developed, wherebya second resist pattern 505A covering the mask-pattern formation regionis produced as shown in FIG. 28(e) or FIG. 28(j).

Thereafter, the phase shifter layer 504 is etched using the secondresist pattern 505A as a mask. As a result, as shown in FIG. 28(f) orFIG. 28(k), the phase shifter layer 504 located outside the mask-patternformation region is removed, and then the second resist pattern 505A isremoved.

As shown in FIG. 28(g) or FIG. 28(l), the light-shielding film 501 isetched using the patterned phase shifter layer 504 as a mask, whereby amask pattern 501A formed from the light-shielding film 501 and havingthe opening 503 is formed. At this time, the mask pattern 501A includingthe opening 503 is covered with the phase shifter layer 504.

As has been described above, according to the fifth embodiment, theopening 503 located in the mask-enhancer formation region is formed inthe light-shielding film 501 on the transparent substrate 500, and thenthe phase shifter layer 504 is formed on the transparent substrate 500.Thereafter, the phase shifter layer 504 located outside the mask-patternformation region is removed. The light-shielding film 501 is thenpatterned so as to form the mask pattern 501A having the opening 503 andcovered with the phase shifter layer 504. This enables the phasedifference to be provided between the mask enhancer and the transparentsubstrate 500 located outside the mask pattern 501A, i.e., thelight-transmitting region. Therefore, the photomask of the firstembodiment can be formed by setting the width of the opening 503, i.e.,the width of the mask enhancer, such that the light-shielding propertyof the mask enhancer becomes at least about the same as that of thelight-shielding film having the same width.

Moreover, according to the fifth embodiment, the patterning step forforming the mask pattern 501A is conducted independently of thepatterning step for forming the opening 503. This enables accuratedimensional control of the mask pattern 501A including the opening 503,i.e., the light-shielding pattern, as well as the mask enhancer, wherebythe photomask of the first embodiment can be reliably produced.

Moreover, according to the fifth embodiment, the phase difference isprovided between the light-transmitting region and the mask enhancer byremoving the phase shifter layer 504 located outside the mask pattern501A. This facilitates management of the etching step as compared to thecase where the phase difference is provided by etching the transparentsubstrate 500. Thus, the phase error is reduced as well as the phaseshifter layer 504 with a vertical edge can be easily formed.

Moreover, according to the fifth embodiment, if defects are produced inthe step of patterning the phase shifter layer 504, it is possible torepair the defects by forming the phase shifter layer 504 again.Therefore, the steps earlier than the step of forming the phase shifterlayer need not be repeated, improving the throughput.

Advantages of the photomask producing method of the fifth embodimentover the conventional photomask producing method, i.e., advantagesobtained by the characteristics of the mask enhancer, are the same asthose of the third embodiment.

Note that, although the fifth embodiment uses quartz glass as a materialof the transparent substrate 500, the present invention is not limitedto this, and calcium fluoride or the like may alternatively be used.

Although the fifth embodiment uses a chromium compound as a material ofthe light-shielding film 501, the present invention is not limited tothis, and a metal such as chromium, silicon or zirconium, a compoundthereof or the like may alternatively be used.

Although the fifth embodiment uses as a material of the phase shifterlayer 504 an SOG film that provides the light transmitted therethroughwith phase inversion of 180 degrees with respect to the exposure light,the present invention is not limited to this, and any transparent filmthat provides the light transmitted therethrough with phase inversion of(170+360×n) to (190+360×n) degrees (where n is an integer) with respectto the exposure light may be used.

In the fifth embodiment, it is preferable that W·0.4×λ/NA, when thewidth of the opening 503, i.e., the width of the mask enhancer, is(W×M).

In the fifth embodiment, it is preferable that L·0.8×λ/NA, when thewidth of the mask pattern 501A including the opening 503, i.e., thewidth of the light-shielding pattern, is (L×M). In this case, it ispreferable that: W·(0.8×λ/NA)−L and W·L or W·L−2E; or0.5×(((0.8×λ/NA)−L)/2)·W·1.5×(((0.8×λ/NA)−L)/2) and W·L or W·L−2E.

MODIFICATION OF FIFTH EMBODIMENT

Hereinafter, a method for producing a photomask according to amodification of the fifth embodiment of the invention will be describedwith reference to the figures.

Note that the modification of the fifth embodiment is different from thefifth embodiment in the following point: in the fifth embodiment, thepatterning step for forming the opening is conducted before thepatterning step for forming the mask pattern, and the phase shifterlayer located outside the mask pattern is removed. However, in the firstmodification of the fifth embodiment, the patterning step for formingthe opening is conducted after the patterning step for forming the maskpattern, and the phase shifter layer located under the opening isremoved.

FIGS. 29(a) to (g) are cross-sectional views illustrating the steps ofthe photomask producing method of the modification of the fifthembodiment, respectively. FIGS. 29(h) to (l) are plan viewscorresponding to FIGS. 29(b), (c), (e), (f) and (g), respectively.

First, as shown in FIG. 29(a), a light-shielding film 511 of, e.g., achromium compound is deposited on a transparent substrate 510 of, e.g.,quartz glass. Then, a resist is applied to the light-shielding film 511to form a first resist film 512.

Then, a pattern is written on the first resist film 512 by using a maskwriting apparatus. The first resist film 512 is then developed, wherebya first resist pattern 512A covering the mask-pattern formation regionis produced as shown in FIG. 29(b) or FIG. 29(h).

Thereafter, the light-shielding film 511 is etched using the firstresist pattern 512A as a mask. As a result, as shown in FIG. 29(c) orFIG. 29(i), the mask pattern 511A of the light-shielding film 511 isformed, and then the first resist pattern 512A is removed.

As shown in FIG. 29(d), a phase shifter layer 513 of, e.g., an SOG filmis formed on the transparent substrate 510 including the mask pattern511A so as to have such a thickness that provides the light transmittedtherethrough with phase inversion of 180 degrees with respect to theexposure light. Then, a resist is applied to the phase shifter layer 513to form a second resist film 514.

Then, a pattern is written on the second resist film 514 by using a maskwriting apparatus. The second resist film 514 is then developed, wherebya second resist pattern 514A having an opening in the mask-enhancerformation region is formed as shown in FIG. 29(e) or FIG. 29(j).

Thereafter, the phase shifter layer 513 is etched using the secondresist pattern 514A as a mask. As a result, as shown in FIG. 29(f) orFIG. 29(k), the phase shifter layer 513 located in the mask-enhancerformation region is removed, and then the second resist pattern 514A isremoved.

As shown in FIG. 29(g) or FIG. 29(l), the mask pattern 511A is etchedusing the patterned phase shifter layer 513 as a mask, whereby anopening 515 is formed in the mask pattern 511A.

As has been described above, according to the modification of the fifthembodiment, the light-shielding film 511 on the transparent substrate510 is patterned so as to form the mask pattern 511A. Thereafter, thephase shifter layer 513 is formed on the transparent substrate 510, andthen the phase shifter layer 513 located in the mask-enhancer formationregion is removed. Then, the opening 515 located in the mask-enhancerformation region is formed in the mask pattern 511A. This enables thephase difference to be provided between the mask enhancer and thetransparent substrate 510 located outside the mask pattern 511A, i.e.,the light-transmitting region. Therefore, the photomask of the firstembodiment can be formed by setting the width of the opening 515, i.e.,the width of the mask enhancer, such that the light-shielding propertyof the mask enhancer becomes at least about the same as that of thelight-shielding film having the same width.

Moreover, according to the modification of the fifth embodiment, thepatterning step for forming the mask pattern 511A is conductedindependently of the patterning step for forming the opening 515. Thisenables accurate dimensional control of the mask pattern 511A includingthe opening 515, i.e., the light-shielding pattern, as well as the maskenhancer, whereby the photomask of the first embodiment can be reliablyproduced.

Moreover, according to the modification of the fifth embodiment, thephase difference is provided between the light-transmitting region andthe mask enhancer by removing the phase shifter layer 513 located in themask-enhancer formation region. This facilitates management of theetching step as compared to the case where the phase difference isprovided by etching the transparent substrate 510. Thus, the phase erroris reduced as well as the phase shifter layer 513 with a vertical edgecan be easily formed.

Moreover, according to the modification of the fifth embodiment, ifdefects are produced in the step of patterning the phase shifter layer513, it is possible to repair the defects by forming the phase shifterlayer 513 again. Therefore, the steps earlier than the step of formingthe phase shifter layer need not be repeated, improving the throughput.

Advantages of the photomask producing method of the modification of thefifth embodiment over the conventional photomask producing method, i.e.,advantages obtained by the characteristics of the mask enhancer, are thesame as those of the third embodiment.

Note that, although the modification of the fifth embodiment uses quartzglass as a material of the transparent substrate 510, the presentinvention is not limited to this, and calcium fluoride or the like mayalternatively be used.

Although the modification of the fifth embodiment uses a chromiumcompound as a material of the light-shielding film 511, the presentinvention is not limited to this, and a metal such as chromium, siliconor zirconium, a compound thereof or the like may alternatively be used.

Although the modification of the fifth embodiment uses as a material ofthe phase shifter layer 513 an SOG film that provides the lighttransmitted therethrough with phase inversion of 180 degrees withrespect to the exposure light, the present invention is not limited tothis, and any transparent film that provides the light transmittedtherethrough with phase inversion of (170+360×n) to (190+360×n) degrees(where n is an integer) with respect to the exposure light may be used.

In the modification of the fifth embodiment, it is preferable thatW·0.4×λ/NA, when the width of the opening 515, i.e., the width of themask enhancer, is (W×M).

In the modification of the fifth embodiment, it is preferable thatL·0.8×λ/NA, when the width of the mask pattern 511A including theopening 515, i.e., the width of the light-shielding pattern, is (L×M).In this case, it is preferable that: W·(0.8×λ/NA)−L and W·L or W·L−2E;or 0.5×(((0.8×λ/NA)−L)/2)·W·1.5×(((0.8×λ/NA)−L)/2) and W·L or W·L−2E.

SIXTH EMBODIMENT

Hereinafter, a method for producing pattern layout and a method forproducing mask-writing data according to the sixth embodiment of theinvention will be described with reference to the figures. Note that thepattern-layout producing method and the mask-writing data producingmethod of the sixth embodiment are the pattern-layout producing methodand mask-writing data producing method for producing a photomask havinga mask-enhancer structure on the assumption that the patterning methodusing the photomask of the first embodiment, i.e., a photomask havingthe mask-enhancer structure (the patterning method of the secondembodiment) is used. In the sixth embodiment, NA is a numerical apertureof a reduction projection optical system of an aligner, λ is awavelength of exposure light, i.e., a light source, and M is amagnification of the reduction projection optical system of the aligner.

FIG. 30 is a flowchart illustrating the pattern-layout producing methodand the mask-writing data producing method of the sixth embodiment.

First, the pattern-layout producing method will be described.

In step S1, the pattern layout of a mask pattern (light-shieldingpattern) to be formed on a photomask is produced.

In step S2, a line pattern having a width L×M equal to or smaller than(Q×λ/NA)×M (where Q is a prescribed value equal to or smaller than 0.8)is extracted from the pattern layout produced in step S1. At this time,a pattern end, pattern corner or another required portion mayadditionally be extracted from the pattern layout.

In step S3, the inside of the line pattern, pattern end, pattern corneror the like thus extracted in step S2 is determined as a position wherea pattern representing a mask enhancer (hereinafter, sometimes simplyreferred to as a mask enhancer) is to be provided.

In step S4, the dimension of each mask enhancer to be provided at thecorresponding position determined in step S3 is set based on thedimension of the line pattern or the like containing the correspondingmask enhancer. Provided that the line pattern of interest has a widthL×M and the mask enhancer provided inside this line pattern has a widthW×M, the value W is set to ((0.8×λ/NA)−L)/2 (where L·(0.8×λ/NA)). Forexample, when the distance between the mask enhancers is smaller than aprescribed value (e.g., the minimum distance required to form adjacentmask enhancers separately from each other), or when the mask enhancersoverlap each other, the mask enhancers are connected together. Moreover,the mask enhancer that is smaller than a prescribed dimension (e.g., theresolution of a mask writing apparatus) is eliminated.

Hereinafter, the mask-writing data producing method will be described.

In step S5, the dimension of the mask enhancers is adjusted so that apattern having a desired dimension can be formed by exposure using amask pattern having the pattern layout with the mask-enhancerarrangement of step S4.

In step S6, mask-pattern formation data corresponding to the maskpattern, mask-enhancer formation data corresponding to the patternrepresenting the mask enhancers, and light-shielding film regionformation data corresponding to the remaining pattern, i.e., the maskpattern excluding the patterns representing the mask enhancers, areoutput based on the pattern layout dimensionally adjusted in step S5.

Hereinafter, steps S1 to S4 (the pattern-layout producing stage) will bespecifically described with reference to FIGS. 31(a) to (d).

FIG. 31(a) shows an example of the pattern layout produced in step S1.

FIG. 31(b) shows the line patterns, pattern end and pattern cornerextracted from the pattern layout of FIG. 31(a) in step S2. As shown inFIG. 31(b), line patterns 601 and 602 having a width L×M equal to orsmaller than (0.8×λ/NA)×M, a pattern end 603, and a pattern corner 604are extracted from the pattern layout 600.

FIG. 31(c) shows the mask enhancers that are provided inside the linepatterns and the like of FIG. 31(b) in step S3. As shown in FIG. 31(c),line mask enhancers 611 a are provided in the center of the line pattern601, as well as end mask enhancers 611 b are respectively provided atthe ends of the line pattern 601. Moreover, a line mask enhancer 612 isprovided in the center of the line pattern 602, end mask enhancers 613are provided at the pattern end 603, and a corner mask enhancer 614 isprovided in the pattern corner 604.

FIG. 31(d) shows the pattern layout in which the mask enhancers arearranged with a dimension as determined in step S4 based on thedimension of the line patterns and the like shown in FIG. 31(c).

More specifically, the line mask enhancers 611 a and 612 having a widthW×M defined by, e.g., W=((0.8×λ/NA)−L)/2 are respectively provided inthe center of the line patterns 601 and 602 of the pattern layout 600which have a width L×M equal to or smaller than (0.8×λ/NA)×M. It shouldbe noted that, in the case where L is smaller than (0.8×λ/NA)/3, or inthe case where a mask enhancer, i.e., an opening, having a width definedby W=((0.8×λ/NA)−L)/2 is to be produced but the line width of alight-shielding film region surrounding the opening would become smallerthan a prescribed minimum possible line width to be produced by the maskwriting apparatus, the line width of the light-shielding film regionsurrounding the mask enhancer is set to the aforementioned prescribedminimum possible line width, and the width of the mask enhancer isdetermined by subtracting the prescribed minimum possible line widthfrom the width of the line pattern. In the case where the width of themask enhancer is smaller than the minimum dimension required to producethe mask enhancer inside the light-shielding region, i.e., theaforementioned prescribed minimum possible line width, that maskenhancer is eliminated.

Note that, in the case of using the photomask producing methods of thethird to fifth embodiments (including the modifications thereof), theaforementioned prescribed minimum possible line width corresponds toabout an alignment margin of the mask writing apparatus.

In the case of using the photomask producing methods of the first andsecond modifications of the third embodiment, the line pattern ofL<(0.8×λ/NA)/3 would provide the same effect as that of the line patternhaving the mask enhancer structure, even if it is formed only from thephase shifter without any light-shielding film region.

In the ends of the line pattern 601, pattern end 603 and pattern corner604 of the pattern layout 600, the end mask enhancers 611 b, 613 and thecorner mask enhancer 614 with four sides of (0.8×λ/NA)/3×M are providedsuch that each mask enhancer is surrounded by a light-shielding filmregion having at least the aforementioned minimum possible line width.In the case where the mask enhancers thus provided overlap each other,or in the case where the gap between the mask enhancers is smaller thanthe minimum distance required to form the mask enhancers separately fromeach other, the mask enhancers are connected together. If the dimensionof the resultant mask enhancer becomes larger than (0.5×λ/NA)×M, themask enhancer is reconfigured so as to have a dimension of (0.5×λ/NA)×Mor less.

As has been described above, steps S1 to S4 enables production of thepattern layout in which a mask enhancer maximizing the light-shieldingproperty is provided in the center of a line pattern having a degradedlight-shielding property and also a mask enhancer is provided in apattern corner and pattern end. Thus, approximately the samelight-shielding property can be realized at least by the portion of thepattern layout having a width of about (0.8×λ/NA)/3×M or more.

Hereinafter, steps S5 and S6 (the mask-writing data producing stage)which are conducted after the mask enhancers and the pattern layoutcontaining the same are produced in step S1 to S4 will be specificallydescribed with reference to FIGS. 31(e) to 31(g).

FIG. 31(e) shows the pattern layout after dimensional adjustment of themask enhancers of FIG. 31(d) in step S5.

More specifically, as shown in FIG. 31(e), in a portion having a patternwidth smaller than the design value as a result of the test exposure(e.g., region R1), the width of a corresponding mask enhancer (e.g., theline mask enhancers 611 a) is increased. On the other hand, in a portionhaving a pattern width larger than the design value as a result of thetest exposure (e.g., region R2), the width of a corresponding maskenhancer (e.g., the line mask enhancer 612) is reduced. At this time, inaddition to the dimension of the mask enhancers, the outer dimension ofthe pattern layout, i.e., the dimension of the mask pattern, may also beadjusted simultaneously. Note that, in FIG. 31(e), the dashed linerepresents the contour of the original pattern layout 600, and the solidline represents the contour of the dimensionally adjusted pattern layout600A.

FIG. 31(f) shows the mask-pattern formation data determined based on thedimensionally adjusted pattern layout of FIG. 31(e) in step S6, and FIG.31(g) shows the mask-enhancer formation data determined based on thedimensionally adjusted pattern layout of FIG. 31(e) in step S6.

Note that, in the final photomask, the mask pattern excluding thepatterns representing the mask enhancers corresponds to thelight-shielding film region, and the patterns representing the maskenhancers correspond to the openings formed in the light-shielding film.

As has been described above, according to the pattern-layout producingmethod of the sixth embodiment, a line pattern having a width L×M equalto or smaller than (0.8×λ/NA)×M is extracted from the pattern layout 600corresponding to the light-shielding pattern, and then a mask enhancerhaving a width W×M equal to or smaller than ((0.8×λ/NA)−L)×M is providedinside the line pattern. Therefore, the mask enhancer capable ofenhancing the light-shielding effect can be provided in the portion ofthe light-shielding pattern having a degraded light-shielding effect,whereby the light intensity distribution can be projected onto the waferwith a less distorted profile with respect to the pattern layout. Thisenables production of the pattern layout of the photomask capable offorming any pattern feature with any dimension including a dimensionequal to or smaller than about the resolution.

Moreover, according to the pattern-layout producing method of the sixthembodiment, provided that the mask enhancer has a width W×M, the value Wis set to W=((0.8×λ/NA)−L)/2. Therefore, the light-shielding effect ofthe mask enhancer is maximized.

Moreover, according to the pattern-layout producing method of the sixthembodiment, a pattern end and pattern corner are also extracted uponextracting a line pattern, and a mask enhancer with four sides of(0.5×λ/NA)×M or less is provided inside the pattern end and patterncorner. Accordingly, the transmitted light reaching the backside of thepattern end or pattern corner of the light-shielding pattern due to thediffraction phenomenon can be reliably cancelled by the lighttransmitted through the mask enhancer.

Moreover, according to the mask-writing data producing method of thesixth embodiment, the dimension of the mask enhancer is adjusted basedon the test exposure result after the mask enhancer is provided so as tomaximize the light-shielding effect of the light-shielding pattern, thatis, after the pattern-layout producing method of the sixth embodiment isconducted. Therefore, the dimension of the mask enhancer can be adjustedso that the dimension of the pattern resulting from exposure becomesequal to the design value. Accordingly, mask-writing data capable ofpreventing withdrawal of the pattern and the like can be produced,whereby a fine pattern can be accurately formed by exposure with thephotomask formed according to the mask-writing data.

Moreover, according to the mask-writing data producing method of thesixth embodiment, the width of a mask enhancer corresponding to aportion having a pattern width larger than the design value as a resultof the exposure is reduced, whereas the width of a mask enhancercorresponding to a portion having a pattern width smaller than thedesign value as a result of exposure is increased. This ensures that thepattern resulting from exposure has a width equal to the design value.

Note that, in the pattern-layout producing method of the sixthembodiment, provided that the width of the line pattern is L×M and thewidth of the mask enhancer is W×M, the light-shielding effect of theline pattern including the mask enhancer is maximized by usingW=((0.8×λ/NA)−L)/2. However, the mask enhancer has a sufficient effectof improving the light-shielding property even when0.5×((0.8×λ/NA)−L)/2·W·1.5×((0.8×λ/NA)−L)/2) (where W L or W·L−2E; (E×M)is the minimum possible dimension to be implemented on the photomask).The mask enhancer has the effect of improving the light-shieldingproperty at least when W·(0.8×λ/NA)−L (where W·L or W·L−2E).

Moreover, in the mask-writing data producing method of the sixthembodiment, the dimension of the mask enhancer is adjusted based on thetest exposure result. Alternatively, the dimension of the mask enhancermay be adjusted based on the exposure simulation result.

1-15. (canceled)
 16. A method for producing a photomask including anisolated light-shielding pattern formed on a transparent substrate thatis transparent to exposure light, the isolated light-shielding patternbeing formed from a light-shielding film region and a phase shiftregion, characterized in that it comprises the steps of: (a) forming alight-shielding film on the transparent substrate; (b) patterning thelight-shielding film so as to form a light-shielding film pattern in thelight-shielding pattern formation region on the transparent substrate;and (c) after the step (b), removing a portion of the inside of thelight-shielding film pattern located in the phase shift region so as toform an opening, the phase shift region has phase inversion with respectto a light-transmitting region of the transparent substrate having nolight-shielding pattern, the light-shielding pattern has at least afirst light-shielding pattern region having a first line width and asecond light-shielding pattern region having a second line width whichis larger than the first line width, the first light-shielding patternregion is provided with a first phase shift region serving as the phaseshift region so as to be surrounded by the light-shielding film region,and the second light-shielding pattern region has no phase shift region.17. The photomask producing method according to claim 16, characterizedin that the step (c) includes the step of etching, after forming theopening, a portion of the transparent substrate located under theopening such that a phase difference of (170+360×n) to (190+360×n)degrees (where n is an integer) with respect to a wavelength of theexposure light is provided between the portion and thelight-transmitting region.
 18. (canceled)
 19. The photomask producingmethod according to claim 16, characterized in that the step (b)includes the step of etching, after forming the light-shielding filmpattern, a portion of the transparent substrate located outside thelight-shielding film pattern such that a phase difference of (170+360×n)to (190+360×n) degrees (where n is an integer) with respect to awavelength of the exposure light is provided between the portion and thephase shift region.
 20. The photomask producing method according toclaim 16, characterized in that the step (a) includes the step offorming under the light-shielding film a phase shifter layer thatprovides phase inversion of (170+360×n) to (190+360×n) degrees (where nis an integer) with respect to a wavelength of the exposure light, andthe step (c) includes the step of removing, after forming the opening, aportion of the phase shifter layer located under the opening. 21.(canceled)
 22. The photomask producing method according to claim 16,characterized in that the step (a) includes the step of forming underthe light-shielding film a phase shifter layer that provides phaseinversion of (170+360×n) to (190+360×n) degrees (where n is an integer)with respect to a wavelength of the exposure light, and the step (b)includes the step of removing, after forming the light-shielding filmpattern, a portion of the phase shifter layer located outside thelight-shielding film pattern. 23-24. (canceled)
 25. The photomaskproducing method according to claim 16, characterized in that the methodfurther comprises, after the step (b) and before the step (c), the stepof forming on the transparent substrate including the light-shieldingfilm pattern a phase shifter layer that provides phase inversion of(170+360×n) to (190+360×n) degrees (where n is an integer) with respectto a wavelength of the exposure light, and the step (c) includes thestep of removing, before forming the opening, a portion of the phaseshifter layer located in the phase shift region.
 26. The photomaskproducing method according to claim 16, characterized in that, providedthat the phase shift region has a width Wm, Wm≦(0.4×λ/NA)×M (where λ isa wavelength of the exposure light, NA is a numerical aperture of areduction projection optical system of an aligner, and M is amagnification of the reduction projection optical system).
 27. Thephotomask producing method according to claim 16, characterized in that,provided that the light-shielding pattern has a width Lm,Lm≦(0.8×λ/NA)×M (where λ is a wavelength of the exposure light, NA is anumerical aperture of a reduction projection optical system of analigner, and M is a magnification of the reduction projection opticalsystem).
 28. The photomask producing method according to claim 27,characterized in that, provided that the phase shift region has a widthWm, Wm≦(0.8×λ/NA)×M)−Lm and Wm≦Lm.
 29. The photomask producing methodaccording to claim 27, characterized in that, provided that the phaseshift region has a width Wm,0.5×((((0.8×λ/NA)×M)−Lm)/2)≦W≦1.5×((((0.8×λ/NA)×M)−Lm)/2) and Wm≦Lm. 30.A method for producing pattern layout of a photomask including anisolated light-shielding pattern formed on a transparent substrate thatis transparent to exposure light, the isolated light-shielding patternbeing formed from a light-shielding film region and a phase shiftregion, characterized in that it comprises the steps of: (a) producingpattern layout corresponding to the light-shielding pattern; (b)extracting from the pattern layout a line pattern having a width L×Mequal to or smaller than (0.8×λ/NA)×M (where λ is a wavelength of theexposure light, NA is a numerical aperture of a reduction projectionoptical system of an aligner, and M is a magnification of the reductionprojection optical system); and (c) providing inside the extracted linepattern a first phase shift region corresponding to the phase shiftregion having a width W×M equal to or smaller than ((0.8×λ/NA)−L)×M(where W≦L).
 31. The pattern layout producing method according to claim30, characterized in that0.5×(((0.8×λ/NA)−L)/2)≦W≦1.5×(((0.8×λ/NA)−L)/2) and W≦L.
 32. The patternlayout producing method according to claim 30, characterized in that thestep of (b) includes the step of extracting a pattern corner from thepattern layout, and the step (c) includes the step of providing at orinside the extracted pattern corner the phase shift region with foursides of (0.5×λ/NA)×M or less. 33-34. (canceled)
 35. The pattern layoutproducing method according to claim 30, characterized in that the step(b) includes the step of extracting a pattern end from the patternlayout, and the step (c) includes the step of providing at or inside theextracted pattern end a third phase shift region corresponding to thephase shift region with four sides of (0.5×λ/NA)×M or less.
 36. Thepattern layout producing method according to claim 30, characterized inthat the light-shielding pattern of the photomask has at least a firstlight-shielding pattern region having a first line width and a secondlight-shielding pattern region having a second line width which islarger than the first line width, the first light-shielding patternregion is provided with the phase shift region so as to be surrounded bythe light-shielding film region, and the second light-shielding patternregion has no phase shift region.
 37. A method for producingmask-writing data of a photomask using the pattern layout producingmethod according to claim 30, characterized in that it comprises thesteps of: (d) after the step (c), adjusting a dimension of the firstphase shift region based on a result of test exposure or exposuresimulation; and (e) after the step (d), outputting phase shift regionformation data corresponding to the phase shift region based on thepattern layout having the first phase shift region dimensionallyadjusted.
 38. The mask-writing data producing method according to claim37, characterized in that in the step (d), the first phase shift regionis dimensionally adjusted and a contour of the pattern layout isdimensionally adjusted.
 39. The mask-writing data producing methodaccording to claim 37, characterized in that in the step (e),light-shielding pattern formation data corresponding to thelight-shielding pattern are output based on the pattern layout havingthe first phase shift region dimensionally adjusted.
 40. Themask-writing data producing method according to claim 37, characterizedin that in the step (e), light-shielding film region formation datacorresponding to the light-shielding film region are output based on thepattern layout having the first phase shift region dimensionallyadjusted.
 41. The mask-writing data producing method according to claim37, characterized in that the step (d) includes the step of reducing awidth of the first phase shift region corresponding to a portion havinga pattern width larger than a design value as a result of exposure withthe photomask, and increasing a width of the first phase shift regioncorresponding to a portion having a pattern width smaller than thedesign value as a result of exposure with the photomask.
 42. A methodfor producing a photomask including an isolated light-shielding patternformed on a transparent substrate that is transparent to exposure light,the isolated light-shielding pattern being formed from a light-shieldingfilm region and a phase shift region, characterized in that it comprisesthe steps of: (a) forming a light-shielding film on the transparentsubstrate; (b) after the step (a), removing a portion of thelight-shielding film located in the phase shift region so as to form anopening; and (c) after the step (b), patterning the light-shielding filmso as to form a light-shielding film pattern in the light-shieldingpattern formation region on the transparent substrate, the inside of thelight-shielding film pattern having the opening, the phase shift regionhas phase inversion with respect to a light-transmitting region of thetransparent substrate having no light-shielding pattern, a width of thephase shift region is set such that a light shielding property of thephase shift region becomes at least about the same as that of the lightshielding film having the same width, the light-shielding pattern has atleast a first light-shielding pattern region having a first line widthand a second light-shielding pattern region having a second line widthwhich is larger than the first line width, the first light-shieldingpattern region is provided with a first phase shift region serving asthe phase shift region so as to be surrounded by the light-shieldingfilm region, and the second light-shielding pattern region has no phaseshift region.
 43. The photomask producing method according to claim 42,characterized in that the step (b) includes the step of etching, afterforming the opening, a portion of the transparent substrate locatedunder the opening such that a phase difference of (170+360×n) to(190+360×n) degrees (where n is an integer) with respect to a wavelengthof the exposure light is provided between the portion and thelight-transmitting region.
 44. The photomask producing method accordingto claim 42, characterized in that the step (a) includes the step offorming under the light-shielding film a phase shifter layer thatprovides phase inversion of (170+360×n) to (190+360×n) degrees (where nis an integer) with respect to a wavelength of the exposure light, andthe step (c) includes the step of removing, after forming thelight-shielding film pattern, a portion of the phase shifter layerlocated outside the light-shielding film pattern.
 45. The photomaskproducing method according to claim 42, characterized in that the step(a) includes the step of forming under the light-shielding film a phaseshifter layer that provides phase inversion of (170+360×n) to(190+360×n) degrees (where n is an integer) with respect to a wavelengthof the exposure light, and the step (b) includes the step of removing,after forming the opening, a portion of the phase shifter layer locatedunder the opening.
 46. The photomask producing method according to claim42, characterized in that the method further comprises, after the step(b) and before the step (c), the step of forming on the light-shieldingfilm including the opening a phase shifter layer that provides phaseinversion of (170+360×n) to (190+360×n) degrees (where n is an integer)with respect to a wavelength of the exposure light, and the step (c)includes the step of removing, before forming the light-shielding filmpattern, a portion of the phase shifter layer located outside thelight-shielding film region.